Caesar will not help you directly to determine wall thickness. You should have this information and much more, before you even consider starting Caesar II.
Pipe wall thickness should be specified in the "Piping Material Specification" or "Piping class".
If, however you need to calculate the wall thickness, take a look in B31.3, it is written there how to determine this (never leave your home without the code:) ).
Normally the nodes have a specific mean (nozzle, restraint, elbow, tee, ...). Caesar can read everything on nodes but not in between. Read COADE Mechanical Engineering News June 2000, page.19. (of course after that read all the documents you can find ). You will understand that sometimes you need a more refined model.