Download the mod or CC files from a trusted source
Unzip the files if they are compressed
Open the Sims 4 Mods folder
Place the mod files in the Mods folder
Keep script mods no more than one folder deep
Open Sims 4
Go to Game Options
Open Other
Enable Custom Content and Mods
Enable Script Mods Allowed
Restart the game
Check that the mod is working
Update mods after game patches
Remove broken mods if the game has issues