Help with network setup, connect modem<-- switch<-- router (DHCP?)

Hi,
I have a problem with my internet setup. I have a switch connected to my modem and when I connect a computer to it everything works. The problem is when I connect a wireless router to the switch it doesn’t work. It doesn’t seem to get the internet connection from the switch. Also when I connect a computer directly to the switch and I use the ipconfig command in cmd, there doesn’t seem to be a gateway address. Anyways I am probably going to get a new switch but I still want to connect it to the modem. And I still need to connect multiple wireless routers to it. And I still need to connect multiple wireless routers to it. Do I have to setup a DHCP server? or are there switches with DHCP. Thanks for your help in advance.