Probably a utube on this, but drill your correct size hole, you need a nut and bolt of appropriate size/thread. Thread nut onto bolt, screw bolt into rivnut, through the thread.
Tighten nut onto top of rivnut, ie as if you were taking it off the bolt. Then hold the top of bolt in a fixed spot and try to take nut off the bolt. This squeezes the rivnut body the same as the pliers and you end up with a good job. (Takes a fair amount of pressure on the spanners with an M6 steel rivnut. ).
I have a quality rivnut tool set at home, but when on the road I carry M4-M8 bolts, a nut and a washer to match each, the appropriate drill bit for each and a small bag of rivnuts (yes, M4 -M8). It all fits into a zip-lock sandwich bag (doubled for strength), little weight and has come in very useful (for myself and others) on a number of occasions.
Useful for the odd riv nut here & there, but the low cost of an air operated riv nut tool if doing a few is well worth the expense if you have an air compressor.