Do you plug in a hose somewhere before setting to back wash an ground pool?

No, you do not plug in a hose before backwashing a ground pool. The backwashing process uses the pool's existing water to clean the filter media. To backwash a ground pool, you will need to turn off the pump, open the waste valve, and then turn the pump back on. This will cause the water in the pool to flow through the filter in reverse, which will dislodge any dirt or debris that has accumulated in the filter media. Once the filter has been backwashed, you will need to turn the pump off again, close the waste valve, and then turn the pump back on to resume normal filtration.