I was working on fb app and was not able to find a way to add app on fan page. Earlier it used to be in app's profile page but now they've discontinued app profile page so only way to add new app to a page is by using the below link.
https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID&next=YOUR_URL
where YOUR_APP_ID is your app's ID and for YOUR_URL I use canvas page URL
You can find more detail below(see Adding an App to a Page section):
https://developers.facebook.com/docs/appsonfacebook/pagetabs/
https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID&next=YOUR_URL
where YOUR_APP_ID is your app's ID and for YOUR_URL I use canvas page URL
You can find more detail below(see Adding an App to a Page section):
https://developers.facebook.com/docs/appsonfacebook/pagetabs/
