hey! this might be a very simple topic, but there are many people who dont know this! So, if you want to add entire albums to your playlist without individually adding each song, then follow these directions!
1. go to the playlist that you want to add, then hit the three dots in the too right corner
2. then, you will see the album code and other settings.
scroll down and hit "Add to playlist"
it will then ask you which playlist you want to add it to, and click that one. You are done! Happy listening!