Lenovo TAB3 8 User Manual page 19

Selecting computer connection mode
You can select one of the following options
Media device (MTP) : Select this mode if you want to transfer media
files such as photos, videos, and ringtones between your tablet and the
computer.
Camera (PTP) : Select this mode if you want to transfer only photos
and videos between your tablet and the computer.
Charge only : Select this mode if you want to stop all USB fuction. Let
you speed up USB charging and decrease power consumption.
USB debugging : Select this mode to enable debugging. You can then
use tools such as Idea Tool on the computer to manage your tablet's
data.
Installing APK
Follow these steps:
You need to set the device to allow installation of apps obtained from
unknown sources.
Go to Settings > Security, select Unknown sources and tap OK.
Copy the APK file from the computer to the device in "Media device
(MTP) " mode.