Rekordbox importing from beatport and exporting to USB

Guys, I'm literally losing my mind trying to do basic functions on Rekordbox. It shouldn't be this hard.

I have tracks purchased in beatport, but its incredibly difficult to find a way to download this stuff I've paid for. 

Furthermore, exporting to a USB is super difficult. I got an error message that said my MP3 tracks are in the wrong format. 

I want to DJ, but I shouldn't have to take a study course to master a software just to manage my music and learn the art of DJing as well