How to setup router for optimum online?

I needed a wireless router so I went to radio shack and got a linksys E3200 high performance dual-Band N router. I have optimum Online. When I try to get on the internet it won't let me. Now it's a very simple way to set up and i did what i was suppose to do but still don't know why its not working. I just want to know how to get it to work.