Which tutorials have you followed? See e.g.
http://quantumwise.com/documents/tutorials/latest/BuilderManual/index.html/chap.move.html for information about the Move Tool.
Basically you just need to build the NO2 molecule and graphene separately, and then drop the molecule from the Stash onto the graphene in the 3D window, and adjust its position, orientation, etc, at least roughly, using the Move tool. Then you need to do a DFT optimization of the system. You should easily be able to find parameters online somewhere to set the molecule up by hand, using "Add>New configuration" and then insert the 3 atoms one by one via the Coordinate List. Since it's a small molecule it's easy to adjust the bond lengths and angles using the Z-Matrix tool, or you can probably find a ready xyz file somewhere that you can import.
I know, it sounds easy but isn't - until you have tried the first time, then you learn it. Most importantly, you can find all these steps (separately, perhaps) in the tutorials.
