Garmin 920xt simple--how do i to reset a lap to 0.00 (Read 38 times)

Hello All and Happy new year!

I just moved to Garmin from an old Polar.

I understand how to use basic screens for different activities, but I can't figure out how to add a lap reset......i.e.  I have run a total of 8 laps, what was the time of lap seven and how do i reset the lap timer to 0:00  for lap eight?  I hit the back button, but have gotten into drill mode etc.  (This was done swimming laps not track work btw)

Does anyone have a simple link to a how to video?  I have looked at quite a few, but maybe this is so basic nobody has demo'd it on you tube!!

Thanks-