A radio bumper, a short advertisement for the radio station itself, sounds like an ideal first radio assignment.  I downloaded a Creative Commons instrumental track from ccmixter to use as the background, then I downloaded and installed Audacity.  With the help of some googling I was able to record my voice and pull in the instrumental track. A little more googling was needed to find out how to cut pieces out of tracks and re-align them.  I exported the result as a WAV file, only to then see that an MP3 file was required.  When I tried to export as an mp3 file I got a message about a missing LAME file.  So I found where to download the LAME files and downloaded them from a site in .ar (Argentina??), virus scanning at every step of the way.  This worked and eventually I created the mp3 file and uploaded it to SoundCloud.