Click on the add-on store icon in the bottom right corner
Search for the Mosquitto broker add-on and click on it, then click on install
After it's finished, click on start
Now we are going to configure the MQTT integration in home assistant, for this, go to setting in the Home Assistant menu and then click on Devices & Services
Click on the Configure button for the MQTT integration and then click on Submit
if everything went well, you should see the following message