Ever set the time on a digital watch?
Same idea:
Hold down both the SELECT button and the ADJUST button until the hours digits start flashing.
Use the ADJUST button to set the hour.
Press the SELECT button to make the minutes digits start flashing.
Use the ADJUST button to set the minutes.
Press the SELECT button to exit the clock set function.
The above was simply what's shown in the Owner's Manual put into my own words.