Assuming you are using a version of Music Maker (MMM) which has a Store tab then see the image below:
Note: do read the terms and conditions of use for the Soundpools, they appear when you click the i icon bottom right as seen in the image above. The default licence is for personal ie non commercial use only.
If you are going create music, using loops, for commercial gain, broadcast etc., then you also need to purchase the Commercial licence versions of the actual Soundpools used in the music that is published for commercial gain.