Here's a bit from their site and a link for the process.
"This is a topic I've brushed on before, but I get plenty of questions about it. So I decided to do a full post dedicated to my favorite fining agent: gelatin. If you ask people their feelings on using gelatin to fine beer, you'll get a number of different opinions. Personally, I find it invaluable to clear my beer quickly. Fining one's beer with gelatin isn't difficult, but it does require a few specific steps. Here's the process I've had success with.
Fermenter or Keg
The first question to ask, is: What state should our beer be in when we add the gelatin? There are two methods, and they both work equally well. You can fine with gelatin in either a fermenter (primary or secondary), or directly in the serving keg. I typically opt for the later. Although, in either case, you want the beer to be cold, and I mean ICE cold. The colder the beer is, the more haze-forming particulate will form. The more haze-forming particulate that forms, the more particulate the gelatin can fine out. I've heard people have used gelatin with some success at cellar temps (50-55F), but I've only had it work well when the beer was at serving temp (32-40F).
Which Gelatin to Buy?
Obviously, you shouldn't buy cherry jello; you're looking for unflavored gelatin. Knox is a popular brand that most supermarkets carry, but I find the store-brand works just as well. Most LHBS also carry gelatin, but they tend to include a hefty markup on the price. The specifics don't matter much, so long as you buy unflavored gelatin, you'll be fine."