Try downloading directly from KODI's website.. Download link's on the first page.

Err.. Use a Web browser on the device itself... No..?

from what i read, this mitv3 has a 5.0 lollipop 8gb android.

but is on own ops sys, not firmwared like sharps and sonys wuth google androidtv which is very easy to use like an android box.

i think there must be a way to sideload android apps.

just google; i think there are users who have successfully rooted it to access the android in full (but mind the warranty, though).

as for kodi, i remember someone with a mitv2 was able to install it in an old thread.

if kodi can be installed, any apk can be installed.