Trimming is the most intuitive thing you can do, it exists only so you wont have to strong arm your joystick to keep your aircraft in straight and level flight.
Trim on a lever is not a good idea tho, its way too sensitive and because of that, it might be better to assign your trim to buttons and use levers for mixture, prop and throttle.
Now back to trimming, pull/push on joystick to keep your aircraft in straight and level flight, add a bit of trim and slowly ease on the controls.
If you still have to pull/push joystick to keep your aircraft in straight flight, add/reduce trim until your plane flying where you want it to, without you applying any force to joystick.
Just don't expect changes to manifest instantly, dont trim too much at one time, give your plane a few seconds before you fill effects of trimming.