Okay so we have to diagnose why the compressor clutch is not kicking in.
You can check your fuses first all.
If the fuse for the AC is okay, then I'd take a hot wire from the battery and try to active the AC clutch by supplying 12V to the connector pins on the AC clutch (not, of course, on the connector you just pulled off).
This is done WITH THE ENGINE NOT RUNNING.
If it does engage with 12V external power, THEN you might try recharging it. It wouldn't take a charge because the compressor doesn't run with the clutch engaged, so it can't take up refrigerant.
As to why the clutch isn't engaging--if the refrigerant has leaked out, then a pressure switch goes off preventing clutch engagement (to save the compressor from damage).
If you have, in fact, lost your refrigerant, then merely putting in new refrig won't solve your problem---you have a leak in the system.