What do you mean by Magix File Browser?

Do you on the Arranger (working area) such as track 1, track 2 or track 3 etc. OR do you want to add you loop to the Soundpool or Media Pool.

Anyway there are two ways

1. To add all supported audio file to the Magix arranger (tracks) click on File Manager then browse where your file is then click on it or drag and drop on the arranger.

2. If you intend to add loop to the Soundpools then it must be inside a folder like Genres Hip Hop, Chillout or Ambient.

Note If you open any folder example Ambient or Hip Hop you will know the difference between soundpool and loop. You can refer tutorial

http://www.magix.info/us/understanding-soundpool.online-training.771235.html

Hope above answer will be helpful.

nihon94