Fungus is definitely not a fun thing to deal with on a lens. There are a couple things that need to be settled before you continue. First, is the fungus on the inside or outside of the lens? Fungus on the outside is pretty easy to deal with, while fungus inside the lens might not be so fun. Next, if the fungus is on the inside, is it a zoom or fixed focal length lens? Zoom lenses have a lot of moving parts and will be very difficult to navigate if you have to open it up.
Anywho, here's how you're going to want to tackle fungus. A solution of equal parts hydrogen peroxide and ammonia applied with a soft cotton swab should kill and remove the fungus, but be sure to work in a well-ventilated area and wear a face mask of some sort. After using the solution, use a microfiber cloth dampened with lens cleaning solution (not the peroxide/ammonia) to wipe off the lens. If you have to open the lens things could get a lot more complicated, and you may consider sending it in to a professional cleaning shop like [http://lensn2shutter.com/fungus.html|this one].
If you don't mind me asking, what lens is it that you're trying to remove fungus from? An inexpensive prime lens may be worth it to try and fix yourself, but a high-end zoom lens might be better suited for a professional.