
The backing is now attached to the spool. This is an open cage reel, which allows for the backing to pass into the cage after it has been attached.
If the reel has a closed rim, you will have to pull the backing through the reel cage before attaching it to the spool, and make sure it's done through the right opening in the reel.
On a ventilated reel like this one, you can also tie the backing to one of the bars in the axle.