Pretty much as BB says. Though if the carboys are both full to the top with only a tiny amount of head space, then they'd probably be fine to leave alone until you decide what you want to do.
Hell, if you're not sure about meads, you can even bottle it into smaller beer bottles, with crown caps. Though if you don't know how long the mead might stay in them, it would be sensible to use oxygen absorbing caps, then fill the bottles to just below the top of the glass, so the liquid won't touch the cap when the bottle sits up right.
I won't suggest how many bottles you might need, you'd have to work that out somehow else - I make my meads to multiples of imperial gallons, which are about 20% larger than a US gallon (1 imp gallon is 4.55 litres, whereas 1 US gallon is about 3.78 litres).