On the iPad photos are stored in the Photos app and those created or edited on the iPad are located in the Camera Roll section and are then available to iWork apps (or any other app) via a Media Browser within each app.
To insert a photo into your iPad Pages or Numbers document, tap the Insert Media icon (upper right - early versions of iOS it looked like a picture, current version of iOS it is a "+" Button) then tap Media - this will provide a menu to chose your photos. Navigate to the photo you want and tap it - a copy of the photo is now available on the document for final sizing and positioning.
Note: Location Services for Pages or Numbers must be ON in your iPad Settings - if it turned off, you will get a warning to turn it on before yoou can access your photos.
You can find detailed instructions for this process and many other operations in the Tools Menu (wrench) Help File for each app.