2004 Volkswagen Golf Water on floor

Ok, this should be fairly simple then.

When you use your AC, condensation builds up on the evaporator, like sweat on a cold glass of tea on a hot summer day.

On the firewall in the engine compartment, find the duct work that houses the heater core and AC evaporator. (It's the big plastic housing)

look for a little tube, or sometimes a short hose, that doesn't attach to anything. It's just hanging there, looking out of place, and probably pointing down.
That's the drain, get a stick or something (i use a metal coat hanger) and try to remove the debris from the hole.
Try not to simply push it back up in the hole, cause it will eventually find it's way back and clog up again.