ATC deviation with FMC

I have many hours of flying, but am new to using FMC's. I've been using the fmc with squawkbox for awhile, but the fmc's with the commercial packages are quite complicated.Before venturing out onto online flying with those FMC's I would like to know if there is a tutorial flight that will deal with ATC deviation apart from what is loaded onto the FMC with FSNav or FSbuild.I am lost as to how to tell the FMC that the route needs to be modified due to vectoring instructions.Can anyone help in this regard? Thank youYou can reply to [email protected]