Tools you will need:
Pipe wrench or equivalent
6 gallon use part #1790610 anode, 12 & 20 gallon use #1790010.
Unthread the hot water fitting. The anode and fitting are one piece.
To install the new anode, clean the threads of the tank, add PTFE tape or paste to the anode threads and install in reverse order of removal.
When refilling tank test for leaks.