First step: Take all the peel and stick tile back to where you got it. It's just a gimmick and it won't hold up. Step two: Two choices. Peel up the backer that the old linoleum is attached to and reinstall new back and apply new linoleum or real vinyl tile with flooring adhesive. Other choice would be to simply install new backer(1/4 plywood without voids) and then install linoleum or real vinyl tile with flooring adhesive. Don't know how big the guest bath is, your budget, or your skill level, but the self adhesive tiles are worthless. Ask anyone else who has had them down for more than a couple of years. Applying them over linoleum is a very, very bad idea.