Remove as much as the paper as you can. Score the rest of it with a wall paper scorer. Mix 1 part fabric softener (any brand) with 3 parts ultra hot water. Pour it over the paper and leave it sit for 15 minutes. If the paper is still thick it will loosen the top layer and help you remove it, then repeat the process. If the paper is thin enough, you can scrap with a wide spackle knife and the paper and adhesive will come up easily.
Rinse with plain water to remove any adhesive or fabric softener residue.