When you say off camera, you mean external, but on the camera?
Its a fairly steep learning curve, you really need to play around with it before hand. With the Nikon speedlights, you can use iTTL which kind of works out the settings for you, or you can try it the hard way and use manual on the flash. Even if you point the flash to 45 degrees and 1/8th power, you should still get ok results.