Welcome Mac! You made a great decision getting a Rialta. When you are at any campground you should always use the shore power (big) cable that came with the coach. There should be enough length to plug into most parks. I have used the extension cord route here at my house when I am too far away from an outlet. The reason to use the bigger cable is the load that is drawn by the Rialta if you would choose to turn alot of things on; which I always do. I run everything on my rig; water heater, fridge, lights, fans, heat or A/C. The biggest draw is on the A/C so you would overload the small extension cord if you did this. For lights or simple things it is safe but that's about it.
Keep in mind that you must plug that back into the outlet inside your storage compartment in order for the generator to supply power to the coach again. Hope I can help in any way so feel free for more questions. It is best to use and operate these vehicles the proper way so you can have the most fun out of it! Once again, welcome and congrats on the purchase!