MQTT Broker no Devices

Hello,
cam someone explain how Mqtt / Mqtt Broker an Tasmota integration works
i have Devices in Tasmota configuration this was automatic in Tasmota.

i want configurate Mqtt broker i want see the tasmota devices in there. i watch many videos an description but nothing works

i have a Sonoff tasmota basic with Tasmota 12.4.0 and i make “setOption19 1” i try the User from HA an i make a new one but no device is appears.
can hepl please