What camera do you have? Does it have a pop up flash? If so it needs to be up to fire your flash. By your quesiton I'm assuming there is no other flash attached to your camera - just your 270 off camera.
If you don't have a pop up flash you cannot fire your 270 off camera unless you get some triggers.
You need to have a master flash to control your 270EX II off-camera. The master flash emits a series of coded pulses of light that tell the 270EX II what to do, how much light to give out etc.
All the following can work as a master flash controlling the 270EX II; Speedlite 550EX, Speedlite 580EX, Speedlite 580EX II, Speedlite 600EX-RT, Speedlite 600EX, EOS 7D, EOS 60D, EOS 600D / Rebel T3i, EOS 650D / Rebel T4i. In the case of the EOS cameras as masters you will need to pop up the flash on the camera and use the cameras menu to set either Easy Wireless flash (on the T3i / T4i) or set the pop up as a master flash on the EOS 60D / 7D.
You'll find some more information on my website here:
Brian / p4pictures