How do you Connect a hub to a hub?
Usually by connecting the uplink port of the first hub to a normal port of the second hub using a straight-thru RJ45 cable. If a crossover RJ45 cable is used to connect them, then the ports at both ends must be the same kind of port (either uplink ports, either normal ports).
Do you have to connect your router to your PC via ethernet cable or can you connect via wifi and do you have to connect your router to your hub?
Yes you acn use a hub to connect your computers. Just connect a cat5 network cable from each of your computers to the hub. It doesn't matter which port you plug the cat5 cable into on the hub. they are all the same. Also, if you might be interested in making your own cat5 cables. I have added a link on how to do ths.