New builders help needed

Building a new computer and having some problems starting it for the first time. Have -Asus p8z77vle mother board

• Thermaltake V02000 Case -i5 3570k(installed for me) -2-4gb ram(installed for me) -660gt

We thought we got it all together but it just won't boot up. A light on motherboard near the SATA connecters is lit green and the lights on the GPU are lit