@ScreamingApe yes. For me, positioning CoM and CoL is pretty much trial and error.

@CruzerBlade CoM doesn't always have to be infront of CoL. Example here

dude you're already on silver, you should know how to use those things.
anyways, I'll explain.
there are three circles:
Red , calculates and measures center of mass (CoM)
Blue, calculates and measures center of lift (CoL)
Yellow, calculates and measures center of thrust (CoT)
.
on building a plane, the CoM should always be on the front of the CoL, but not too far or the plane will become unstable
CoT is much less forgiving, it doesn't need too much attention. unless if you're building a VTOL plane or a heli. on measuring CoM and CoL on a heli, it's much more trial and error, so you should never give up trying again and again
.
if you still doesn't understand, check out SP's ground school level.