Sorry, I was busy and didn't answer to your question in the "legal music" forum. I usually try to continue answering if I start. Though, better this way. This is the correct forum.
A: Select the APL files.
You must have a single APE file (includes the audio data of a whole audio CD disc) and several APL files (one for each track). They must be in the same folder (usually, there can be exceptions). Import just the APL files to Media Center. (E.g. by this way: select them in Windows Explorer > right-click > select Media Center > select Import.).
Inside Media center you can convert the APL files to MP3 format if needed. APE (and APE & APL combination) is a lossless audio format. The audio quality is exactly the same with the original source. You can play APL files directly in Media Center and also burn Audio CDs. MP3 is a lossy format.
By the way, there is no MC10 beta. MC10 is the current version. MC11 is at the alpha stage (beta soon?). Perhaps you mean that you are on the 30-day try out period.