How do you locate the low side service port on a 1994 ford ranger?

Larger hose from compressor to evaporator

Umm, you just described the whole system lol.

I believe the service port on that year of ranger for the low side will be right on top of the accumulator on the passenger side of the engine compartment. The systems works starting from the Compressor as a high pressure vapor, then goes to the condenser and gets changed to a high pressure liquid, then goes to an accumulator (or a receiver drier on some systems, which would be after the metering device), then to the metering device where it gets metered down to the evaporator, which turns it back into a low pressure vapor, then back to the compressor where it gets re-pressurized back into a high pressure vapor for the process to start back over again.

Hope this helped!