Are your songs not tagged? If you have set title and artist info on the songs, they should be found automatically.
Before repairing the link I would recommend you first add missing title and artist info and then repair the link. That way you will prevent this problem from reappearing.
If you tap on "Repair link" you select the matching song in the iTunes library. No need to add that song afterwards.
Unfortunately this step can not be automated as each song needs to be reassigned individually. If there would be some automatic way, the app would do it automatically by itself. See here for details why this happens: https://support.stagetraxx.com/d/500-missing-songs