My monitor won't start

I bought this computer yesterday with a Acer al1716as monitor and tryed to set it up with my limited knowledge , after I started it up the Acer logo appered on screen follwed by the words no signal the screen then goes black and the green light on the monitor turns orange, I've no idea what the problem is and have only tryed switching the monitor off and on again, the pc stays on and seems to be running, there are a few wires and a grey box that came with the computer that I haven't used and don't kmow what they are, if any one can help i would be grateful thanks.