I need to know what connections i need to connect two computers to one hp printer

A 5 port switch (Hub) and network cables are about the simplest.
If the printer doesn't have a network port, you can add a small print server.
The print server is a little device the connect to the parallel port on the printer.
You then connect it to one of the ports on the switch (Hub)

Another way to share a printer is to connect the printer to one of the computers, and then share it. This is considering that you have the 2 computers networked together.
The drawback with this setup vs the first one, is that the computer that has the printer attached, must be on for the other computer to be able to print to it. The first setup, you only need to have the printer on, for either computer to be able to print to it.