There's an easier way that sometimes works:

• Open your Chrome browser and make sure you are logged in the same account as your Mi Box
• Turn on your Mi Box
• Go to the google store and find the app you want on your Mi Box.
• Click the install button. A drop down will come up.
• If your Mi Box is available to be selected, select that and then hit install
• Go over to your Mi Box and your app will be installing instantly.

This method doesn't work for all apps. Sometimes the Mi Box will be grayed out in the drop down list.

Check out #SIDELOADTAG here:

https://play.google.com/store/apps/details?id=tv.puppetmaster.tinydl

And a list of already created tags are available here:

https://plus.google.com/u/0/communities/116227013726118171272

You can create your own by linking to your Google drive apk using the direct link generated here:

https://sites.google.com/site/gdocs2direct/

And then paste it into tinyurl.com to create your own #sideloadtag. Then enter it into the app and voila.

You should be able to send any file from phone to mi box via Bluetooth.

After you sideload Airdroid you can use it to remotely manage and install apks.

download mixplorer from xda and download the apk u want from apkpure. in mixplorer start an ftp or http serverband on the mi box use totalcommander or chrome to open it and install the apk.

A previous version of es explorer allowed for access to web urls

Do you have a desktop/laptop? You can easily use a USB drive to transfer the apk to the Mi Box

And if you have a USB OTG adapter for your phone, I think you can use that to transfer the apk also

Air-Share is useful for sideloading. https://play.google.com/store/apps/details?id=com.blackspruce.gloo