Hello,

You'll need a kit, available at Wal-Mart/Auto Zone/similar. The kit will contain a method of attaching a can of freon to a valve, a hose and gauge, a connection that puts the freon into your system. The freon goes into the Low pressure port, which is the larger line at your compressor, and the cap should have the letter "L" on the top of it. NEVER add freon to the high pressure port. It is on the smaller line and will have the letter "H" on the port cap.
When you take the low pressure cap off, there is a schrader valve (bicycle tube valve) under it. You'll connect a can of 134a to the manifold/valve in the kit, and fit the hose onto the low pressure valve. You screw the valve on the manifold all the way in to puncture the seal of the can, and then slowly open the valve to dispense the freon. Nothing to it. Now start your vehicle with the windows down, and the A/C set on high, with the fresh air option set to fresh (not on recirculate).
Get the type of kit that has the gauge built into it, so you do not wind up overfilling the system. Dispense the freon with the can valve up, so you don't put liquid freon into your compressor.
Then, watch the gauge until it gets in range. Close the valve on the can, shut your vehicle off. Remove the hose quickly to avoid freon loss. Replace the valve cap. Chill!
Your kit will come with instructions. Read them. Most kits do not come with freon. Buy two cans, three is better. You don't want to run out of refrigerant in the middle of charging the system and have to go get more.
You should have no trouble putting freon in your system. Just be mindful where you place your hands and equipment,and you'll do fine.

Best regards, --W/D--