Yes, Audacity will do it, but it's a clart . . . .
Plus you'll have to separately download and install the MP3 conversion program - it's open source so not as joined up as commercial software.
First, load up (Open)) your first track, I presume it's MP3. Then load (Open) your 2nd track and when it's on screen Ctrl-A to select all. Ctrl-C to copy, then go back to your first track, press End which will take you to the end of the first track, then Ctrl-V to paste your 2nd track on the end of your first track.
Then you'll need to drag the cursor between 2 points in your compiled track which will highlight the section, then press Delete to remove the unwanted portion which should be the portion between the end of the first track and the beginning (or first beat) of the 2nd track.
So in plain english, copy the 2nd track onto the end of the 1st and delete any gaps then save as MP3. Obviously, getting the beat to be continuous without a stutter is a skill you may have to master.