Problems with D-Link Wireless Router

Hello, I'm having trouble with my D-link wireless router. My original set up was AOL Broadband's DSL modem connection(ethernet). The model number is DI-624. After I've properly set It up, I still can't connect to the internet. I've had a friend who has the exact router and had aol dsl help me, but he's stumped now too. I've entered my username and password in the PPPoE box, and I've changed the MTU to 1400. I've never worked with wireless routers before, so I'm not too bright on them. I bought It so I could use Nintendo's WiFi, help me please. I don't know If other information Is needed so I can be helped, so just ask. Thank you.