How to use a nikon sb-800 flashgun with a nikon D3000 camera?

I have been given a sb-800 flashgun to use with my camera so i can take photos at a graduation but as iv never used a flashgun be for can someone tell me the basics for using a sb-800 fashgun please?

Take a look at the manual for the SB 800 speedlight.http://www.nikonusa.com/pdf/manuals/Speedlights/SB-800.pdf

Do this indoor, preferably with another person.
Switch off camera and flash
Mount flash on camera making sure the locking lever is in position.
Switch on camera and flash
Set camera to A mode, iso 400 and aperture f5.6 Fire a picture with the flash head forward. Now shoot a picture. Do the same with the flash head up 45 and 60 degrees. Now repeat with the diffusor on it.

Look at the pictures, see the differences.