There are a few ways to do this. One is to use a product called wallcovering adhesive, which you can buy at any hardware store. This adhesive comes in a tube and you put it on the back of the wallpaper before you hang it up. It's very easy to use and it will make your wallpaper look like new again. Another option is to use paint or a wallpaper border to cover up the torn areas. If you choose this option, be sure to match the color of your paint or wallpaper border with the color of your walls so that it looks seamless.

Well, first of all, you'll want to make sure that the walls are clean and free of any dust or debris before you start. Once they're clean, you can apply a coat of primer to help the wallpaper stick better. Then, apply a coat of your wallpaper adhesive to the wall and carefully place the new wallpaper over top, smoothing it out as you go. If there are any tears or creases in the paper, just use a little bit of wallpaper paste to repair them. Let everything dry completely before moving on to the next step. Last but not least, paint over the entire wall with a fresh coat of paint to hide all evidence of your DIY project!