Thank you for you reply but my problem it's i don't have the message box to authorize the mix box, it's work with my shield tv.
I tried to plug/unplug and activate/deactivate the usb debugging but nothing
Do you hear a sound when you plug/unplus your usb cable from the PC?
If not, try another usb cable or different usb port on your PC. Also check you have the correct Windows drivers, but that should be virtually automatic.
You may have missed the authorize dialog. I think you can reset the auth process by making the appropriate selection in the Developer options of the settings menu.
Using USB to install an app is over complicating things. Install es explorer as I suggest above. This will have the added benefit of allowing you to form a network connection to your pc where you can save your backups.
While you are on apkpure site, also grab a file called app cloner which will let you create a 'Leanback' compatible version of almost any sideloaded app and it will appear in the Leanback launcher for easy access.
The ideas above will let you install apps until you can resolve your usb debug issues.
NB, it would be wise to get an actual mouse or a remote mouse app on your Android phone/tablet to permit navigating sideloaded apps that require clicking, which is not part of the leanback experience.