dumb new guy question

I dont have the OEM firewall.
the car has a GM style hardware installed top front/rear and lower rear already from when i bought the car, but no net came with it.

I'll have to figure out how to attach it to the front lower section too... I assume there was a cable tying it to the floor that had an eye-bolt ??

I've never looked at how they are attached to the lower front part.

any pics of how you guys did it?