BAsically you're boiled the carcass to get the flavour off.
So for stocks you'd add carcass (plus any manky unedible bits) then onion, carrots, few herbs (bay leafs are usual), pepper. Boil for a couple of hours (or bung all in slow cooker and I leave for about a day on med or low). No need to peel veg for stock as you fish them all out anyway.
For freezing, either freeze as it is or reduce and reduce (by boiling high so you boil the liquid off - can't do this in slow cooker) till it coats the back of a spoon. Then freeze in ice cube trays. Can't remember what it's called but it's bascially concentrated stock, so takes up less space as you only need one or two cubes.
I don't add salt to it, cos then you got salt free stock for the kids.
Soups, do basically the same except peel the veg if you are adding, and don't forget to fish the carcass out after.
recipe for chicken stock here Has others on site too.