To now, it’s not been possible to customize your Android TV device to show your apps in the order you want them. That changes with the latest update.
Download and install this APK (update can also be found in Google Play), head to Settings > Home Screen > Apps & Games and you’ll find a new option for choosing between recent apps or a custom order. Enable custom order, and all you’ll need to do to reorder your apps is long pressing the one you want to move.
Use the navigation buttons on your remote of choice to place it where you want, then hit the save button. Voila. You’ll also be able to cancel the change, or drag the app to a trash icon to uninstall it. Be sure to try it out as soon as you can if this is something that can benefit you.