Need to add 134a to 2000 S-10

This is my first Chevy and I'm not familiar with the A/C layout. I need to add refrigerant, but I don't know which line to use. The only line I see is marked for "evaporator service", but my hose doesn't fit snug to it. The only other place that the hose will fit is on the condensor itself and that sure doesn't seem right. Where/what am I missing? I've looked all over and just don't see it. Thanks, Paul