Wall preparation is key for a successful installation. Clean your wall with a humid cloth at least one day prior installation. You wall must be free of humidity.
If you wall paint is peeling off, use a wire brush or paint scraper to scrape off all loose paint. You will need to paint the wall at least 3 days before installation. For maximum adherence, you can paint with gloss/semi-gloss paint.
Your wall must be dust free. Before installation clean your wall with a cloth. If your wall isn’t fully clean then the wallpaper is going to adhere to dust instead the wall. Meaning: peeling off and peeling corners.
Why is all this so important? You are investing some money and time, don’t waste it. With a little effort, you are installing a wallpaper that won’t peel off.