I need to charge the AC in a 97 Buick Skylark... Where is the low pressure port located?

I have everything and I am ready to go. I just can't seem to find the low pressure port to add the refrigerant. Can anyone tell me where it is located or even better send a picture?I need to charge the AC in a 97 Buick Skylark... Where is the low pressure port located?it is the bigger pipe of the two.coming from the firewall. the high side will be the smaller pipe that goes from the condenser at the front of the radiator to the evaporator,usually underneath the low side pipe. don't make a mistake between the two as it can cause an explosion resulting in allot of pain or even death