While holding this shield, you can speak its command word as a bonus action to cause it to animate. The shield leaps into the air and hovers in your space to protect you as if you were wielding it, leaving your hands free. The shield remains animated for 1 minute, until you use a bonus action to end this effect, or until you are incapacitated or die, at which point the shield falls to the ground or into your hand if you have one free.

Unfortunately, this item doesn't seem to show anything under bonus actions on my character sheet. I end up forgetting that I can activate it because of that. Can that be fixed?

Actions have not yet been added to Magic items. They are working on that, but it could be days or years.

In the meantime you can add a “Custom Action” directly to your character sheet, name it for the shield, and designate it as a Bonus Action.

Ahh, that's too bad. Thanks for the tip though, I'll do that!