what you have is a heater core (which is like a mini radiator)between the
drivers compartment and the front passenger compartment under the dash
near the feet. Basically a black plastic "box" with a split in the
middle. It is located inside there. Hopefully you won't have to go
there.
Lets first look beside the accelerator pedal. On the firewall right
behind it you should see 2 rubber hoses. That is hot water in and out to
the engine. Where it comes in, it then goes to the back of the "black
box". You may need to take the seat out as you will be getting your head
down at the pedals.
Just before it goes into the "box" there should be 2 hose clamps that
you can tighten. Hopefully, fingers crossed, that is where the leak is
at.
If not, then I would suggest getting a library book on VW
repair(Rabbits, Golfs -don't really matter they are basically the same in
construction) and read up on heater core removal(for now the heater core
has sprung a leak) which you can either get repaired at a rad shop or
score another at a salvage yard) New costs are terrible.
If you do the job yourself, You will be pulling the seats(so that you
have some room to work. If you are a heavy set fellow, woe beit to
yourself.
A number of hand wrenches(metric)10&13 and a screwdriver and a needle
nose plier and you can do it.
Better if you get the book for the pics are worth a thousand words.