[IanH]

This could be a variety of things.
Check that the clutch is not engaging by eye. the pully spins but the center remains stationary.
If the Freon is low the low pressure switch opens and prevents the clutch from Engaging.
So either check with a meter sw is ok or gauges check for Freon pressure.

 

[IanH]

No you must not jump the clutch, if you do you risk destroying the compressor.
The compressor uses freon to carry the Oil, if there is no pressue, ie no freon, there is no Oil to the moving parts.
You must charge the A/C so the pressure switches are made, then the compressor will work.
This is not a problem, the can of Freon is at high pressure and just flows in when connected up to the system.

 

[IanH]

The clutch is at the belt end of the compressor.