You’ve got a couple options here. See which works best for you.
To attach the organizer to the seat:
Simply feed the flap of the organizer through the slit in the fabric on the back of the seat and velcro to secure.
To attach your organizer to the handlebar:
You’ll use those velcro straps to connect your organizer’s loops to the handlebar on each side. Flip out the loops (discreetly tucked into the front pocket) and secure each one to the handlebar with a strap so the organizer hangs suspended below. Pro tip: You can adjust where the straps sit on the handlebar to raise or lower the organizer to the best height for you.
Oh, and your phone charger lives in the inner pocket of the organizer to keep you charged up while you’re on-the-go.