This article includes a 1:15 video walkthrough.
Quick answer
The decorative upper back panel is held on by four snaps, one near each corner. With the upper back removed from the chair, slide a butter knife gently between the panel and the back at each corner and pry back to release the snaps. To install a new panel, line it up and press each corner in, one at a time.
Step by step
Remove the cuff, nut, and bolt, and take the upper back off the chair (see "How do I remove or install the upper back pad?").
Use a butter knife or another dull-tipped tool so you don't cut the fabric.
At each of the four corners, slide the knife a little way between the panel and the back and gently pry backward until the snap releases.
Lift the panel off.
To install, set the new panel in place and press in all four corners one at a time. Don't rush it.
Also called: upper back cover, back panel replacement, damaged upper back panel, decorative panel.
Video transcript
This is how you take your upper back panel off. Now, you've taken the cuff off, you've got the nut off, and you've taken the bolt out. You have your back in your hand. Now you need a magic tool, and it's called the butter knife. This is how you get the job done.
There are snaps underneath here that hold this decorative panel on. All four corners: right about here, here, here, and here. All you've got to do is lightly, gently, with a butter knife so you don't cut your fabric, just slide it in between the two a little bit. It just has to go down a tiny bit underneath there, and you just pry backwards. There's one. There's two. Three. Four. And now the panel is loose. You just grab it, and it comes off. And you can see those clips right now.
Now you're going to be putting on your new panel, and you're going to do the same thing but in reverse. Set it back on, and we've got to get all four corners. So don't go quick. Just do it one at a time. One, two, three, four. Perfect.