To Install Rooftop tent, you need to have roof platfom:
or a pair of cross bar like:
https://centorioutdoors.com/collections/accessories/products/centori-2-pieces-heavy-duty-rooftop-cross-bar-set-fit-46-to-53-span-across-raised-side-rails
Check below condition:
1, Cross bar or Platform needs to have 1.5 inch space over the car roof;
2, The distance between the cross bar, should be more than 60% of the whoe lenth of the RTT.
3, If you use the cross bars, make sure it is heavy duty can support the required load weight; Platform normally could support more than RTT requires,
4, Check how long your car roof is, make sure the lenth will comparable with the lenth of the RTT you choose, if not sure, just shot up an email, we will answer your qeustion with other clients' experiences
5, Be aware of the spots if your crossbars directly lands to the car roof, on the vertical beans, it supports more weight than the roof itself.