Welcome aboard.
For what it sounds like you want you simply need to use traditional overlay construction (see the help, reference manual, or knowledge base)
In attached image all cabinets use traditional overlay.
The ones on the left are simplest and only require traditional overlay (36" cabinet, wide top rail, increased reveal)
Middle cabinets us a molding to extend tops up (36" cabinet extended top rail)
Two cabinets on the right use a custom door symbol. (36: cabinet extended top rail) This is the only advanced method) see post I made in tips section on "cabinet hacks" if you want to go that way. I don't explain it , only put examples that you can open. Open the symbols and cabinet DBXs to learn from.
Lastly not included here you can use "blank areas" to create reveals. I do that with cabinets that list a "0" reveal and usually "0" separation for the construction. Then all reveals and all separations are added manually. This is also advanced and will require a bit of trial and error to learn.
Going forward it's a good idea to fill out your signature with software version ans system information. Makes it easier to answer some questions.