Dennis,
This depends on hte radio. By the way you've asked the quetsion, i'm guessing you have a 6X. Assuming you do...

when you are done flying,
with the transmitter still on
go to trim memory screen
move ALL trims you DO NOT want to save to center (if you don't put ht throttle trim to center onw you will memorize how ever much trim you hvae in the throttle right now)
store the trims as described in the manual, pushing the desired buttons (sorry no 6X in my hands)
move the trim sliders back to center.
now you can see little arrows above or below the channels who have a trim position stored.
you MUST put the sliders back to center and NOT do the accept command a second time in the flown position or you will double the trim stored!

If this doesn't help, or if you have a different radio, please provide more details.

the 8U, 9C and 9Z have no need to memorize the trims -- digital trims remember the trim position for each model automatically and don't need to be moved.

WELCOME to computer radios and happy flying!