I don't mean to be a weinie but if you don't know where the oil drain plug is, perhaps you shouldn't be changing the oil? It is a pretty basic task.
Look for a reatively large round plug with a pretty large allen (12mm
I don't recall, I just grab what fits) It is the bigger of the two that you will see.
You will also want to pull the oil screen and check/clean it. It is the plug on the right side of the engine that has a wire hooked to it. Once that plug is out, you will need a 14 mm allen (rather large and not usually found at Wal Mart) to remove the screen...Check FAQ on this Board...should be help there?
I remember reading a post here not too long ago of a guy who torqued the screen plug to the spec for the oil drain plug and he cracked his engine case.....Soooo changing the oil can lead to problems if you are not sure what you are doing.
That 14 mm screen was really in there tight on my machine the first time I changed the oil on my S2r...be aware.
It is an easy task but if you are not very mechanically inclined, you may want your dealer to do the first one.
L.T. Snyder's book on Ducati maintenance would be a great help too.