AR142 Aluminum Zinc Anode Rod

How do you replace a nipple style secondary anode rod that leaks around top?

Can this replace rheem wh anode or, complicating things for me, does it go in water inlet/outlet pipe as i read in your q&a?

I installed the anode rod very tightly but it’s still leaking at the top. (it’s very tight). cut to size. what’s the problem? needs plumbers tape, or?

Is this anode rod made of a combination of aluminum/zinc/tin? Or just aluminum/zinc?