You hook it up to the faucet to drain as well. Do you still have paper instructions? You attach just as if you are filling, but turn water on cold and pull down on the attachment drain. It sucks it right out.
I submerge the hose and let the water drain out in the main tube halfway and start to drop it down. I then tip it so tha water starts to get sucked in.
I do as BlueIZ does. only I leave the shut-off open until water reaches that level so it will purge air from the line and then I close it and finish filling the line. I let the remainder of the air purge out the top of the tube and when full I stick tube back in tank and then open shut-off. It's easier than it sounds.
I drain mine into the yard also since I am on a septic and don't want to add unneccessary water to it. Yes the faucet drain works well. The pumping up and down is for the birds.