Spackle over wallpaper backing
Unlike Joe- I have found few walls that weren't totally ruined, that couldn't be revived. But it takes a bit of skill.
Again, without seeing what we're talking about, I would get a wallpaper razor scraper and get off as much as I could (without causing further damage)-
Then I'd prime - either with oil or my favorite- Gardz- to seal the whole mess and get a starting point-
Skim smooth, sand prime , look over and spot mud as needed, sand and prime those- paint.
With practice this process is not as daunting as it sounds, but to a newbie at it it is asking much.
"It's better to come here with questions before you screw up than to come here after and ask how to fix them."- JS