1. Remove the panels of the machine.
2. Locate the expansion valve.
3. Remove the hose from the top of the expansion valve. It may be stuck on there so you might need to use a pick to free it up and slip it off. If you are only adjusting the expansion valve you won't need to pull the hose off.
4. Remove the top of the expansion valve. You will get some water coming out of here so you may want a towel handy.
5. Use a pair of needle nose pliers to remove the expansion valve seat after taking out the spring. From here you can clean or replace the rubber seat if it needs it.