The jacks have sufficient capacity to hold you and the full camper up on their own. Typically you would lower the camper to ease the stress on the jacks and make access easier. Some people add support under the floor if the camper does not have a basement or if they are trying to minimize any movement while they are inside.
If you load the camper on a truck or trailer, you can lower the jacks to help stabilize the camper rather than have it move on the suspension and tires. Normally you would lift it just enough to slightly unload the truck's rear suspension but not enough that the camper would clear the bed. If the ground on which you have the camper set is uneven, you will want to remove the camper tie downs so you can level camper and let the truck only be semi-leveled.
In my area, campers must be screened from street view if kept on your property and no one is allowed to live in them unless your property is zoned for multi-tenant use.