|If you have two Internet connections you are going to need two routers and connect them to the switch. If you connect your Broadband Modems direct to a switch, only one computer will be able to use each Internet connection at a time.|
Bear in mind that any one computer will only be able to use one Internet connection at a time unless you buy a dual-wan router with load balancing.
How you set it up depends largely on what you want to achieve and how many client computers you have. Do you want all the client computers on the same networks so that they can communicate with each other or two completely separate network.