Yes, the hose going into the water pump would be the return from the heater. The heater supply hose would come from or near the thermostat location.
The engine heaters that go into a heater hose should be plumbed into the hose that goes to the water pump, with the arrow pointing at it, in most cases. Otherwise, the heater stays hot, while the engine isn't kept as warm, since the coolant would have lost most of the the heat by the time it got to the engine.