First off, welcome to the forums!
I'm assuming this is a pop up aka pup. You may wish to also check over at the popup portal. There are lots of great folks over there with specific knowledge of pop ups. Oh course also stick around here.
The steps to dry are
Stopping more water from coming in
Getting fresh air circulating around the wet stuff.
I'd crank up the roof and have it fully set up to air out.
Was the entire roof covered with a tarp? How did the previous owner have it stored? Does the roof look intact? Are there any cracks?
2017 JayFlight 21QB
2021 Ford F150 SCrew 3.5 Eco, 157Ē, 3.55, Tow Pkg