i have a lot of experience with lead acid batteries.
charge it up as best you can with a good charger.
if it is a fairly new battery, then it hasn't had a lot
of time to sulfate.
charge it but don't let it overheat, if it is too hot to touch,
then let it cool down then charge it some more.
charge it till the ammeter shows a low current level.
lead acid batteries hate being discharged completely.
my other car has the battery it came with 7 and 1/2 years
ago and has been discharged similar to your description.
if it charges up to a low current draw level and will start your
car easily, then don't worry about it.
if it has been discharged a while, it may take a while before
it draws any current to speak of when charging
if it won't hold a charge, then it's time to get a new one.
make sure something in the car isn't pulling it down.
if it takes a day to charge it don't worry.
just get it charged up again as soon as possible.