Drain Fresh water prism 24CB

[pepe456789]

Hi!
New to rv and bought a 2021 prism 24 CB.

I feel so dumb:

- how do I put vinegar solution in fresh water tank to sanitize? Trying to avoid bleach.

Tried by gravity with hose on water hookup... nada.....

Even dumber:
Low drain point seems to be under kitchen sink.... but where? So I can drain my fresh water tank fully...

Sometimes.... I was proud of my PDI list
Not so much
Missed a very basic one.

Thanks for any help you may have!!