It is possible. I had the same problem. What you need to do is the following:
- Categorize your existing page under “App Page” (found under “Brands & Products”).
- Change your page name to mach your App name.
- Go to your App and select “App Details”
- Under “Contact Info” you will find “App Page”. There you will be able to create a new page or if all went well, select your page from a list.
I found the info in the little question-mark next to “App page”.
I hope this helps.