How to link a Facebook app with an existing fan page

Solution 1:

It is possible. I had the same problem. What you need to do is the following:

1. Categorize your existing page under "App Page" (found under "Brands & Products").
2. Change your page name to mach your App name.
3. Go to your App and select "App Details"
4. 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.

Solution 2:

It is possible to add the application to any page you administer. This can be achieved from solutions mentioned below:

Solution 1

http://facebook.com/add.php?api_key=[YOUR_APP_KEY]&pages=1&page=[YOUR_PAGE_ID]

YOUR_APP_KEY You can get it from application settings, its App Id

YOUR_PAGE_ID You can get it through Graph Explorer https://graph.facebook.com/[PAGE_NAME]

Solution 2

https://www.facebook.com/dialog/pagetab?app_id=[YOUR_APP_KEY]&next=[REDIRECT_URL]

YOUR_APP_KEY You can get it from application settings, its App Id

REDIRECT_URL Any URL you want to redirect back to after adding the tab

Official Solution
Answer from @Dvir Levy is the official solution from Facebook. The issue with that approach is that we mostly can not follow that solution. Suppose we had to add an application tab to a brand page like 'ABCXYZ', if we follow that answer then we had to change the brand page name, and we can't do it, brands/clients we work for doesn't allow these changes.

Solution 3:

Due the recent changes on the Facebook UI, some options have changed or are under a different place.

I would like to share the up to date way to achieve this.

On your page

1. Access the About section
2. Click on Edit Page Info on the top right side.
3. Set one of your categories to App page

PS: May be needed your page and app share the same name, but can't confirm this.

On your app

Access your app from the Facebook Developers apps panel.

1. Access Settings on the left side menu.
2. Set the category to Apps for pages and hit Save. [@JohnMc mentioned this has to be the only category selected.]
3. Open the Advanced section and find the App Page block.
4. Under Existing page select your page and hit Save.

All set!

Note: If you remove the link between the page and the app you won't be able to link them again.

Edit: As @John Mc pointed out in the comments, App page has to be the only category selected.