I have a 99 ranger xlt, 4.0l 6 cylinder one of my heater hoses has a hole in it, not sure if it is the inlet or outlet

 

One end attaches to the heater core

Where on the engine does the other end attach ?

 

Attaches to bottom of engine

 

If its on the water pump then its the return line, from heater core(or heater core bypass valve)
Upper intake near upper radiator hose is the out to heater core(or heater core bypass valve)

You should reverse the 2 hoses on the firewall heater core nipples every 2 years to reverse flow inside the heater core, this will help it last longer