Locate the low pressure air

Follow A/C lines,only one will fit,second is bigger.

The caps are generally different sizes, the recharge hose from the can, will only snap on to the correct one.

The low and high side valves are located under the air filterbox, if you open the hood and remove the air filter box you will see the valves ,good day

Needs ComPresser

FOLLOW THE AC COMPRESSOR LOW PRESSURE TO THE ACCUMULATOR AND EVAPORATOR LINE GOING INTO BACK LOWER FIREWALL LOOK FOR A LINE WITH A BLUE CAP ON IT.THATS YOUR RECHARGE PORT.

The Low Pressure Side connector will be smaller than the High Pressure Side connector so the refill hose will fit properly only on the Low Pressure Side.
Read more: How to Recharge Air Conditioning with Freon in a Dodge Ram | eHow.com http://www.ehow.com/how_4484569_recharge-air-conditioning-freon-dodge.html#ixzz0uLCDkUE8

The Low Pressure Side connector will be smaller than the High Pressure Side connector so the refill hose will fit properly only on the Low Pressure Side.
Read more: How to Recharge Air Conditioning with Freon in a Dodge Ram | eHow.com http://www.ehow.com/how_4484569_recharge-air-conditioning-freon-dodge.html#ixzz0uLXJnwvE

The low pressure switch is located on the accumulator.

Your system may be low on R134a and needs to be recharged, If you did recharge it with the recharge kit and you over charged it, you'll have poor a/c performance too. The low pressure side should have 30psi to 50psi and the high pressure side should have 150psi to 200psi, any other readings will give low a/c performance and if to high of pressure can lead to system damage. Good luck and hope this helps. 

You will need R134a, and a filler hose. Charge the system on the low pressure side, it should have a blue cap on the charge point.
Your filler hose will only fit the low pressure side, just in case the cap has been removed.