Above responses are true, but I'd also add that if you have more than a few clicks of trim on any surface ((3 or 4 or more) then you should mechanically adjust the linkage to retrim the plane.
Good advice.
The 6EXA is so easy to use. Once you select the model you want to fly (1 of 6), you can access the trim settings screen, or each time you adjust the trims, the trim screen will appear briefly, showing the new setting. Fly your model and trim it as needed. The cool thing about electronic trim is the beep! It's nice to have the audible reference while you are flying. Once trimmed, your settings are in that models setup memory. Each time you select that model to fly, your settings are automaticlly applied, and if changed, automatically saved. As stated above by DBCherry, you should adjust the linkages so that you can set your trims back to 0.
Hope this helps.
Jim C