you will find that it's neccesary to adjust/tighten the steering lines occaisionaly, especially when lines are new as they will stretch a bit.
As said previously, remove the black cover at rear and all will be pretty obvious re loosening line holding screws, then retightening.
I also have a second handle fitted instead of the steering knob.
My handles are about 1/2 off being perfectly centered but don't find it an issue anymore.
Adjusting the steering lines to the same tension will improve the alignment.
When seated, they look a little "out" even when striaght. You will get used to it, or go insane
Check your manual to be sure on the process.