You'll have to play around with the MOVE/INSERT and CUT (remove part) operations on Page 59 of the manual. These will let you move one or the other backwards or forwards to align with the other. Just pick one track and move that around until it's start point matches the other track's start point.
The easiest way would be to use a DAW in your computer, but it's even more complicated to move them from the DP-008EX to the computer. Doing this in your DP-008EX is easier than it looks. It's just matching up numbers instead of visually aligning audio waves.