Guide to Modding Stardew Valley

SMAPI

Go to smapi.io to download SMAPI, following the instructions for Github or Nexus Mods (or use Curseforge if you prefer).
Extract the zip file into your downloads folder (or anywhere else, it doesn't matter). Open the SMAPI installer folder and select the install on Windows.bat file.
From here there a series of prompts. If you use Steam you can select 1 here.
$Where do you want to add or remove SMAPI? [1] C:\Program Files(x86)\Steam\steamapps\common\Stardew Valley [2]Enter a custom game path. Type the number next to your choice, then press enter.$
For the next prompt you should also select 1, if you are updating SMAPI this will also delete any old copies while it installs the new one.
What do you want to do? [1] Install SMAPI. [2] Uninstall SMAPI. Type 1 or 2, then press enter.
And that's it, SMAPI is installed. The installer will then tell you where to put your mods and how to launch your game.
$SMAPI is installed! If you use Steam, set your launch options to enable achievements (see smapi.io/install): "C:\Program Files(x86)\Steam\steamapps\common\Stardew Valley\StardewModdingAPI.exe" %command% If you don't use Steam, launch StardewModdingAPI.exe in your game folder to play with mods.$
To change your launch options in Steam, right click on Stardew Valley in your library and select properties. The option is under the general tab and you can paste C:\Program Files(x86)\Steam\steamapps\common\Stardew Valley\StardewModdingAPI.exe" %command% in there.

Finding Mods

Here are some mods I recommend to get started:

Browse the internet for other mods that suit your play style or preferences.

Downloading Mods

This can differ slightly depending on where you get your mods from. These are the instructions for the places I normally download from.

Nexus Mods

On the page for the mod you want, first click Manual next to download options. A row of buttons. The first four read add media, track, endorse, and vote. To the right there is text that says Download: and next to that are two buttons that say vortex and manual respectively.
There may be a popup that tells you that additional files are required. If you have already downloaded these you can ignore this and press download. Otherwise you can either open these links in new tabs to download after or you can download now and then go back to the requirements after.
The popup looks like this:
A popup from Nexus Mods saying additional files are required for the mod to run. It warns that you need other files installed before running the mod and lists the mods as hyperlinks.In the bottom left corner there is an orange download button.
And the mod requirements are found here and look like this:
A screenshot of the description tab on Nexus Mods. The screenshot includes the other tabs, the about, and the requirements and permissions dropdown menus. The requirements table on Nexus Mods. It lists the mods required and notes about them, and in a seperate table lists the mods that require this mod.
Some additional mods are optional depending on what you do with the mod, such as the Sprites in Detail mod shown above.
The download button will take you to this page with the option for fast or slow download.
A table comparing free and premium download types. At teh bottom there are buttons that say slow download and fast download.
Fast download requires paying Nexus money and most mods are small enough that the fast download speed is unnecessary. For the few larger mods, such as DSV or SMAPI, you just need some patience.
There may be a 5 second wait before your download begins but once it starts you can continue downloading other mods or move onto installing.
Text reading "Your download has started. If you are having trouble, click here to download manually."

ModDrop

Underneath the title of the mod there will be these buttons, click download.
Three purple buttons reading Install with ModDrop, Download, and Options respectively.
There may be a dropdown menu with different options, if you know which version you need you can select that from the list, if not click see all versions.
A dropdown menu under Download with 2 file option and a button that says "See all 3 Versions"
This is what the all files menu looks like. To select a version click on the title.
A list of 3 different files for the Solstice Winter Star mod.
You may have a popup when you select a file. The file will begin downloading when you click OK.
A popup with a message from the mod author telling the user that the mod they are downloading requires another mod to run.

Github

On Github just click on the zip file (in this case the first one) and it will begin downloading.
A list of assets on Github.

Installing Mods

To install mods you need to take all the mods you've downloaded from the downloads folder on your computer to the mods folder for stardew valley. This path will show up in your SMAPI window when you install it and is probably similar to or the same as C:\Program Files(x86)\Steam\steamapps\common\Stardew Valley\Mods. Drag your mods still in their zip files to the mods folder and extract them one by one. Once a mod has been extracted you can delete the zip file. When they're all done you can play the game with your new mods.
If you get an error that says the file path is too long, you can just shorten the folder names, it doesn't change how the game uses the mods. For example most mods include teir version in the folder name but if the path is too long you can simply delete that part. As long as you know which mod it is and don't mess with the manifest.json file inside, you'll be fine.

Updating Mods

Follow the same instructions for downloading, then go to your mods folder and delete the old version of the mod before following the installation instructions. If the mod contains a lot of customisations, such as Diverse Stardew Valley, consider creating a copy of the config.json file so you can transfer the data easily.

More info

Stardew Valley Wiki's Player Guide to Getting Started with Modding