Nikon Flash Help Needed

So i have a nikon d7000 and i just got a nikon sb 600 flash. I can't seem to figure out how to make the flash work remotely. The flash works perfectly fine when attached to the hotshoe but doesn't seem to work off camera. For some reason i can only make it flash remotely when i have my pop up flash up. When i put the pop up flash down it doesn't flash. Does anyone have a d7000 with a speedlight or know how to solve this?

You have to have the camera's flash up. That allows the camera (via flash) to signal the remote flash.

If you set the remote channel up properly, and if you put in a blank value for the camera's flash, you will still see a flash from the camera's flash as that is a signalling flash to the SB600.

But the flash intensity from the built-in flash is low, and will not contribute to the lighting of the image.

And the best way to test it is to put the remote flash at a good angle (say 45deg) from the camera and try it. You should see that the direction of the flash shows the remote flash is illuminating the subject and not the camera flash.

There's nothing that needs to be solved - that's just how it works.

The popup flash is used for the communication between camera and external flash. It sends its control signals *before* the actual photo is taken, so the control signals themselves don't affect the exposure.

You might have the exposure affected by the popup flash when it fired for a second time in TTL mode. On the control menu of the flash where you can adjust the exposure for the remote flashes you also can deactivate the popup flash or set it to a desired exposure.
If you deactivate it, then it will still fire the signals to the other flash units, but that will be before the photo is taken and thus not be visible on it, as already mentioned.