I know I'm not Jan, but I'll try to answer as far as I know.
Aileron trim is used when for whatever reason your aircraft is abnormally banking to one side or another. Then you use aileron trim - there are two switches. BOTH must be operated at the same time (one gives power, the other gives ground to the actuator). And the only indication is the phisical movement of the control wheel (on the yoke) and it will change the neutral position which you can read from the scale on the top of the yoke column.