I have a neewer tt560 speedlite for my nikon d3000, how can i work slave mode?

I have a d3000 from nikon and a newer tt560 speedlite and only manual mode works on the camera, but S1 or S2 (slave mode) doesn't work when I take a picture. How can I make this work so the flash will come on?

The D3000's on-camera flash can't be used as a commander.

Did you use the popup flash of your D3000 to trigger it, or did you just put it on these slave modes and did not use the popup flash of your camera? You must do the former. The flash does not magically know when to fire, it needs your popup flash to be triggered. This usually also only works in closed rooms.
If you already did use the popup flash, did the tt560 flash fire but didn't seem to have an effect (a synchronization problem) or did it do nothing?

@Taylor
While the D3000 popup flash can't be used as a commander for Nikon TLS, it should suffice for
triggering "dumb" optical slaves such as this one. I use the popup flash of my D90 in normal mode, no commander mode, to trigger a Yongnuo 560 flash.