adjusting front suspension (trek 3900)

[physique]

I'm new to MTBing. (Been riding for about a year now)
I got a Trek 3900. The previous owner is about 40lbs lighter than me.
(Same height though)
I need to know IF and HOW to adjust my front fork suspension. I don't
know if they need to be adjusted or not, but I figure the bike should
be adjusted to my 230lb frame. Can anyone advise on a "how to" link
where I do the repair/tune up myself? Thanks a lot.

-Physique