How do I remove the middle agitator thing in the machine?

there are a few different types. Yours may just have a large square hole in the middle under the cap,the "special" tool you need is a socket extension bar (available at most department stores and hardware stores)or a very large flat screwdriver. Insert the tool in the square hole and unscrew it. It is really a bolt. After you take the bolt out lift the top half of the agitator off.You should find a second bolt to remove. This will remove the bottom half of the agitator. There is some more information about it on here and if you still have trouble, give us your serial number so we can try and find out how to get you going.....Good Luck