My parents are out of town and when I came to check on the house I went to the restroom and flushed, it wouldn't no water was in the tank, I have heard my dad talk about sometimes he has to prime the pump, I'm wondering how I do this?

My parents are out of town and when I came to check on the house I went to the restroom and flushed, it wouldn't no water was in the tank, I have heard my dad talk about sometimes he has to prime the pump, I'm wondering how I do this?
Ok, shut the power off to the pump at the breaker box. Now look on top of the impeller cage and seea small 1/4" threaded plug,( sometimes a gage is installed in it's place), Remove the plug,or gage, and fill the openb hole until water runs out. Replace the plug/gage and turn the pump back on. This should restore the pumps prime. If it's impossible to fill the impeller cage then you have a faulty check valve and it must be replaced. Good luck, Tom