How do I install brackets to roof so I can tie down stuff?

If you're taking it to burningman, drilling a few screws into the roof and the potential leaks down the road are probably the least of your rv damage worries! Lol
Otherwise, you'll want to find the framing layout for the roof or it'll pull out of just the sheeting.
With the wind though, just make it breakaway. Clip the tarp to the gutter with some little pony clamps, spring clamps.