That’s not right. By default, an MQTT user is created called emonpi with a default password, but I would create a login for Home Assistant by connecting with ssh and using the command
sudo mosquitto_passwd /etc/mosquitto/passwd homeassistant
and then
sudo service mosquitto restart
to make sure it detects the new user (reload instead of restart may suffice but I’m not completely sure). Then put those details into HA and it should connect.
I think you’ll also want to add some “Publish to MQTT” steps to your input processors but maybe there are other ways.
Good luck!