Basically when you log on to NWBC you can get the list of user roles which helps you to start the user interface.This user roles are already defined in NWBC.
In PFCG you can go to change mode to enable adjusting the role menu and then navigate to tab-Menu.Here you can define your own folder substructure to define your own menu area that will contain FPM based application.Here once you click -create -New folder and then you need to follow the instruction .
Once you add FPM based application then you can control various authorisation for web transactions.
In case you are interested to control sccess via POWL pplication, you need to use Tcode-POWL_TYPER and this will assogn POWL type to PFCG role and hence users assigned to this role will be able to see new POWL