You don't need a router but you do need to use the 'phone to create a Hotspot then let computers join the network that the Hotspot makes.
Tap the Apps square then Settings>More networks>Tethering and portable hotspots. Name your hotspot and give it a strong password then let the PCs into the secret.
I think you will soon find that the speed will be very slow and will get worse the more devices share the connection.