Just use caution when placing the vacuum plate over the skimmer basket. Make sure the opening that the hose connects to is NOT above the water level or you will pull air in, and have to disconnect and wait for your pump to reprime.

I say this because on my pool the plate opening is above the water level even when my water level is high.

I connect the plate to the already hose after I fill it with water from the return and it's already connected to the vacuum head and pole. I then lift the plate into the skimmer and place it.

Also - as a side note: You can leave the main drain valve opened until after you have everything connected up. That helps reduce the suction lower until you are ready to start vacuuming. Once you are ready turn off the main drain to ensure you have maximum suction.

Good luck!