Hello there, thanks for reaching out.
I assume you're talking about adding an album to a playlist right?
In that case you go to the playlist.
Click on the 3 small dots you see inside the playlist.
From the list that pops up, click on "Add to playlist" and then choose the playlist you want to add to.
Hope that's helpful, take care.
Hey there you, Yeah, you! 😁 Welcome - we're glad you joined the Spotify Community! While you here, let's have a fun game…