Sorry I don't use Music Maker to check, but the specs say it can import mp3 files. For Magix video editing programs you can import by dragging a file onto the timeline from a Windows Explorer window or from a 'media pool' provided in the program.
The shot above (from http://www.magix.com/au/music-maker/detail/) shows an empty track area -- you would probably use a free track if the mp3 selection is reasonably long. Below the timelines look like a media pool of loops sorted by instrument type etc. Check if you can change that to show your available mps or wav files.
I'm sure regular MM user will have more to say when they wake up! I've jumped in with the advantage of being out of sync with most of the world's time zones! :-)
Have you tried Help from the top menu bar? Try a search for mp3 or import.
If I am not wrong, first you must not be using Magix Music Maker in normal mode, if you can see below Soundpools, File Manager or File Browser, Templates, etc. it means you are in advanced mode. Now to import any supported audio format click on File Manager/File Browser tab and browse the place where your desired audio is saved. When you found the file click on it and drag and drop on the arranger(the empty track).
What is a normal mode or what audio format is supported by your Music maker version refer Help file.
Who cares if a topic is 4 years old or a newer version has been released since. If someone found a fix to their problem, it might shed guidance for future people that stumble across this topic troubleshooting their own same issue -- like myself. Even if the old version was fixed one way, someone may be able to be guided in the right direction by using that info as a reference.
But now, because you have deterred anyone from "resurrecting an old topic" you've now caused me and anyone else that reads this further searching in order to find what could have been disclosed right here.
@Hails I also have this issue, and I thank you for asking for the missing information that was not disclosed in this thread.
@phardy68 If you remember what you did to fix your issue, I'm sure someone would appreciate the follow through on the topic.
If you have an issue then post a new topic given the information requested in my post above.
Music Maker has had 2 new interface designs and several changes in the default behaviour of parts the program since the release of MX .
Referencing a new version to an old one such as MX introduces further complexity to resolution of an issue due to the changes in the newer versions, thus increasing the frustration in try to fix an issue.