Basically you just plug the module into an outlet near your router and plug a cat 5 between the module and a free port on the router. If your router doesn't have any Ethernet LAN ports you will need to add a switch after the router or get a new router with Ethernet LAN ports. Then plug the remote module into a garage outlet following Netgear's instructions for finding the best outlet.
My garage has an electrical subpanel but it is fed from the house panel. Powerline can be tricky and I had to try different outlets to find the best performance. The netgear modules has LEDs on them to show you how good the signal is.
Throughput is highly dependent on the distance between the modules. The model I used has a max specified speed of 500mbps, which it nearly got when both modules were used in the house itself as a test. But because my range is fairly long (over 100 feet) and goes through two power panels I only get 80mbps in one direction and about 38mbps in the other. However the connection is very solid and has been good enough to use on demand from my garage hopper without network issues.
If you try this I'd buy the modules from someone with a good return policy. You cannot predict how well these will work without trying it and you may have to send them back.
Good luck.