Hook the top into slots in cappings at desired locations.
Push seat frame back until the baseplate is flat with vehicle body, or wherever you are wanting it.
Do note if the bolts will have to run thru the wheel arch support members. You will need longer bolts if so.
Then buy the lap belt kits for 18 bucks or so, install.
* if you have no net worth or assets, feel free to put people in without seatbelts.