This document explains how to get a list of Page access tokens for Facebook Pages a person using your app manages.
The following code example, exchanges a User access token for a Page access token. Using the User access token, a list of all Pages the User manages is returned. This list includes Page access tokens for each Page. You can then use the Page access token to get information about the Page, such as page_fan_adds insights.
These Page access tokens are valid for 1 hour.