need help setting up a router with AT&T DSL

sorry to post such a lame question on here, but I'm really struggling setting up my router with my AT&T DSL modem. I found a similar post, but couldn't figure out how to do what they were saying. I'm kind of a computer idiot, but from what I can tell there are some serious problems setting up routers with AT&T modems. I have a Motorola modem and a Linksys BEFSR41 router (wired only). When I set everything up, my computer says that my connection is working fine, but then I can;t connect to the internet at all. I'm a total noob when it comes to reconfiguring IP addresses and stuff like that. Can someone help me in terms that my computer-illiterate brain can handle. Thanks in advance, and sorry again to the noobish post.