iTunes can't play music from moved iTunes library (in TM backup)

Hi,
So I have an iTunes library on an external Time Machine drive I want to play in iTunes. (The TM is for a computer I don't have access to at the moment.) I can open the library fine via option-opening and selecting the library on the TM disk. All playlists appear correctly, but none of the music can be played because the "original file could not be found." How do I make iTunes find the files?

Edit: Resolved, had to go to the advanced tab and point to the library from there.