Id like to know if my nikon d90, can be used with my off camera flash wirelessly?

I have a Metz 48 Af-1 flash, and a Nikon D90. I would like to know how to set it up off camera for flash,. If its possible.

If your Metz is the model made to work with Nikon, you turn on the optical slave in the flash and you turn on the optical controller in your camera. See both manuals for specifics on how to do this. If you don't know, check the pinout in your camera's hot shoe. One large contact with 4 small contacts… The arrangement of the 4 small contacts much match on the bottom of the flash. If it doesn't, then the flash is not Nikon compatible.

If your flash is dedicated to another brand like Canon, then you must use cheap radio triggers off EBay and set the flash in manual mode, requiring you to adjust the flash power yourself. Your camera must also be used in manual mode to accommodate the flash.

The Metz MC15 macro flash can. I'm not sure about the Metz 48.

On the Metz MC15, there was a setting for manufacturer; Canon, Nikon, Sony, etc. Which put the flash into wireless/TTL mode for that brand camera.

Then if the flash has this function, you then have to set the channel and group to your desired settings (try Channel 1 and Group B).

Then on the D90, put the camera into commander mode and set the same channel and group.

Here is a video tutorial on how to setup a D90 and SB700 for wireless remote use.

If the Metz unit supports this function, the procedure for the D90 would be the same (as it knows not if you have a Nikon or Metz flash), but the setup would be different for the Metz flash.

You'll have to consult your flash manual for setup.