If your wallpaper is damaged, you can try to fix it by patching it with some adhesive. However, if the damage is too extensive, you may need to replace the wallpaper entirely.

If the wallpaper is peeling or bubbling, you can peel it off and apply a new coat of wallpaper adhesive. If there are any big holes, you can patch them up with some spackling paste. Finally, use a brush to apply a thin coat of wallpaper sealant over the entire surface. Let it dry for 24 hours before hanging new wallpaper.