Winterizing pool lines

I just closed my pool for the first time.

I was told to blow out the lines until I saw boubles. I saw them and plugged the pening. I amconcerne though that the water level may not be low enough.It is just slightly below the skimmer but not below the water returns and water lines. Since I saw the boubles is it ok to leave the water levels above the water line openings?

I am also juggling through the same difficulty!