Leaky water spigot in barn

We just replaced the water spigot in our barn about a month ago, a couple of weeks ago it started leaking so a friend of mine tightened it up and it was ok except it was very hard to open and close the handle. A couple of days ago it started leaking again, I've tried to tighten it but since I don't really understand how it works I'm probably not doing it correctly.
This is the kind of faucet that is frost proof with the big handle that pulls up to let the water out. I've tried to find a diagram of it online but no luck so far.
Please help, at first it was only dripping but now the water is actually running out of it, almost like it's only shut off half way.

Thanks,
Anna

You may have to unscrew the mechanism and pull it out to stop the leak, but, if I understand properly, if he tighten the "packing nut", that would not have stopped water from leaking out of the faucet, but WOULD have made it harder for the spring to close the valve. LOOSEN the nut a bit to see if it is gripping the stem too tightly for it to close.