Owntracks only for battery level, not for geolocalization. Using MQTT

Configuration
1

Hi i need to track battery level of my wall mounted tablet.
So i don’t need geolocalization and I can use my local MQTT mosquitto on my Raspberry.

After some research I see Owntracks is the best way but I don’t find how to configure app on my tablet.

In my configuration.yaml i’ve this:

mqtt:
  discovery: true
  broker: 192.168.2.5
  port: 1883
  birth_message:
    topic: 'hass/status'
    payload: 'online'
  will_message:
    topic: 'hass/status'
    payload: 'offline'

Can someone help my how to configure app on my tablet? i don’t undestand some fields to compile