Installing a custom app

Ensure you have latest platform-tools installed in the system.

Enable Developer Mode by tapping Settings->About Phone->Build Number multiple times.
Enable Settings->Developer options->USB debugging
Check if the unit is connected

$ adb devices
List of devices attached
66c4bfea    device

Install app using adb install <app_name>.apk

$ adb install myapp.apk
Performing Streamed Install
Success

Your app should show up in the app launcher's list.

To remove the app do adb remove org.myorg.appname

$ adb remove org.myorg.appname
Success