Easiest way to do this is to ensure both pcs are connected via the cable.
Run the network setup wizard (NSW) on the PC with the internet connection. Chose the option that says the other computers get out Via your pc. This pc will get the IP address 192.168.0.1
On the second pc run the NSW, this shoiuld spot the shared internet connection, so say you want to use it. Just ensure this pc has a different name but the same workgreup.
Should it not spot the connection, if you right click on the network card in network caonnection and chose properties, The double click tcp/ip the IPaddress should be 192.168.0.2, subnet mask 255.255.255.0
default gateway 192.168.0.1 and prefered DNS 192.168.0.1