Install SMAPI
Install a code editor like Visual Studio or VS Code
Install the .NET SDK version required by your SMAPI version
Create a new C# class library project
Reference the SMAPI and Stardew Valley game assemblies in your project
Set the project output to a mod folder structure
Create a `manifest.json` file
Add required manifest fields like `Name`, `Author`, `Version`, `Description`, and `UniqueID`
Create a main mod class that inherits from `Mod`
Override the `Entry` method
Use SMAPI events like `GameLoop`, `Input`, `Display`, and `Player`
Add your custom logic in event handlers
Build the project
Copy the compiled DLL and manifest into a mod folder
Place the mod folder in the `Mods` directory
Launch the game through SMAPI
Check the SMAPI console for errors
Test and debug your mod
Update the mod when Stardew Valley or SMAPI versions change