First you put the the GarageBand Project back onto the GarageBand Documents area of you iTunes File Sharing section and make sure your iPad syncs with iTunes.
Now in GarageBand, go to the My Songs window, click the + button and select "Copy from Tunes". You should see all the GarageBand Projects that are available in your iTunes FIle Sharing section (from step 1). Tap on it to copy the Project to the My Songs window.
Now you can open it.Hope that helps
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