As scorpion said
The process would be SOMETHING like this (im not near my computer, so this is best guess)
hf 14a sniff
Place the Proxmark between the acess system and the card being WRITTEN, or possibly read.
After it has written to the card, press the side button of the Proxmark (this stops the sniff)
hf 14a list
This should spitout the communication between the reader/writer and the card, amogst which will be the password.
I am not super familiar with the process, those could be the old syntax commands, but that is the general principle, which should be enough getting you down the right track to getting an answer