Download and install the correct mod loader for your Minecraft version (Forge, Fabric, or Quilt)
Download the mod files (.jar) you want to install
For Forge/Fabric/Quilt, ensure you have the correct Minecraft version installed in the launcher
Close the Minecraft launcher
Open the Minecraft game folder
Windows: `%appdata%.minecraft`
macOS: `~/Library/Application Support/minecraft`
Linux: `~/.minecraft`
Create or locate the `mods` folder inside the game folder
Copy the downloaded mod `.jar` files into the `mods` folder
Do not install mod files into `versions` or `bin`
If the mod requires additional dependencies, install those dependencies the same way (as `.jar` files in `mods`)
Start the Minecraft launcher
Select the profile that matches your mod loader (Forge/Fabric/Quilt)
Launch Minecraft
Confirm the mods loaded successfully in the main menu (mods list) or in-game (mod screen/logs)
If Minecraft fails to launch, remove the last added mod and try again to identify the incompatible file