how do i put in refrigerant in airconditioner. low side has pressure comming out.

not sure what you mean exactly...the shroeder valve is leaking?

if there is a leak, fix it first or you'll just be wasting money, and tenniisshoes is right. there should be pressure on the low side....to recharge your air conditioner, you need to have your vehicle running with the ac on high. take the cap off of the low pressure valve. You can get recharge kits that have a hose with a gauge built into it (that will just clip right on to the valve the same way accessories hook up to the end of an air compressor hose) Turn the can upside down and shake it while pressing the button on the top of the can. and simply stop when the gauge tells you that the level is good. Be sure to wear gloves while doing this as the can will get extremely cold.