Summarize:

Well water filers just sit inside of the housing, so there aren't any clamps to unhook. Grasp the top of the filter and pull it straight up to remove it from the housing. Dump any excess water out of the housing after you've removed the filter. Check the ends of the new filter. If it needs to go in a certain way, one end of the filter will say "top" and the other end will say "bottom." Make sure the end with "bottom" written on it goes into the housing first. On the top of the housing, you'll see the o-ring, or the round piece of rubber that guarantees a tight seal between the housing and system. Take the o-ring off of the housing and check it for dings, flat-spots, or holes. If you find any, you'll need to order a new o-ring. You should be able to get a new o-ring from the same place you purchased your new filter. Use a food-grade silicon grease to lubricate your o-ring and the o-ring groove in the housing. Squeeze some of the lubricant onto the o-ring and rub it all the way around. Replace the o-ring and then squeeze a bit more lubricant into the o-ring groove in the housing. Rub some silicon around the threads on the housing, too. You can find food-grade silicon grease at most home improvement stores or online. The top of the housing will have threads at the top, where it will screw into the filtration system. Line the housing up under where it screws into the system. Once you have the housing lined up, begin rotating the housing counterclockwise. As you do so, it will screw into the system until all of the threads on the housing have disappeared and it won't spin anymore. Then use the filter wrench to tighten it some more. Chances are the outside of the housing got a little wet while you were changing the filters. Use a soft cloth to wipe down the outside of the housing and remove any excess moisture. Once the filter is changed and the housing is screwed back in, you can turn the water back on. Watch the housing carefully if water starts to leak out of it, you haven't tightened the housing enough. Turn the water off, tighten the housing, and then turn it back on.
Remove the old filter from the housing. Insert the new filter. Check the o-ring. Lubricate the o-ring and threads of the housing. Line up the housing with the system. Screw the housing back into the filtration system. Wipe down the housing. Turn the water back on.