Licensing aside a larger issue is handling the bigger rig. It is somewhat (depending at what level your driving skills are to begin with) intimidating to put yourself in that captains seat for the first time.
Find a local less traveled road in that area where you're picking it up and spend a couple of days on it.
Learn the controls and anything technology wise...slow things down (baby steps)...learn to use your side/west coast mirrors. In a big rig you should be in a constant state of awareness of everything around you. And know that the rig itself should be monitored for fluid leeks...tire condition etc, The #1 rule of thumb when a situation arises slow everything down and leave the hwy as safely as possible.