Just went and had a look at mine - I do believe the cover has to come off first.
It seems there are two slotted tabs from the center portion that protrude through the bumper skin, then on each side a small blue part that inserts into the slots from the front, holding the smaller part into the bumper cover. You may be able to reach through the holes and push these out, but I don’t know how you’d get them back in after you install the new part.
If you get a flashlight and look up from the ground toward the center under the whole bumper you should be able to see what’s going on.