Download the custom content file from a trusted source
If the file is compressed, extract it using a zip or rar tool
Open the Sims 4 Mods folder
On Windows, go to Documents > Electronic Arts > The Sims 4 > Mods
On Mac, go to Documents > Electronic Arts > The Sims 4 > Mods
Move the custom content files into the Mods folder
Keep script mods and package files in the Mods folder
Do not place custom content deeper than one folder level if possible
Open Sims 4
Go to Game Options
Select Other
Enable Custom Content and Mods
Enable Script Mods Allowed if needed
Restart the game
Check the in-game custom content notification
Verify the content appears in Create a Sim or Build/Buy mode