You cannot directly add PS4 friends to Steam as Steam friends
Add them through the game’s cross-platform or cross-play friend system if the game supports it
Link your PlayStation Network account to the game or publisher account if required
Use the in-game friend code, username, or ID system to send a friend request
Make sure both accounts are set to allow cross-play and cross-platform friends
If the game uses an external launcher or account system, add friends there instead of in Steam
If the game does not support cross-play friends, you cannot add PS4 friends on Steam