Problem with sound on DDJ-S1 - Please Help

I plugged in the DDJ-S1 into my computer, the AC adapter is also plugged in; installed Serato Itch, then installed the latest driver (downloaded from Serato's website). I'm using RCA cables (monster); from my DDJ-S1 output 2 plugged directly into my M-Audio AV-40 monitors. The problem is when I play a track on Serato, there is no sound coming through the headphones or my speaker monitors. However, when I boot up my computer the windows chime sound comes through my headphones, and only the windows chime. When I try to play music on youtube through my headphones, there is no sound. Please help, i want to start mixing already.