Sharing an internet connection using a switch

I am attempting to share internet between two windows-based PCs. I have a Netgear FS105 Fast Ethernet 5-Port Switch. I have only ever networked using a router. The internet connection is a adsl dhcp provider. Whe I plug everything into the correct ports, I get an IP conflict on one of the computers. One works. One doesn’t. I have rebooted the modem and the router. Restarted both the computers. Tried different ports. It says on the box that I need network management software. I didn’t know what I should do. Thanks!