Connecting MQTT publisher to HA UI

Configuration
1

I have an AdaFruit ESP32-S2 setup to publish temperature data via MQTT. I’ve setup MQTT in HA as far as I can tell.

How do I define an entity / device associated with the MQTT broker that can display the published value?

(I thought EspHome would be a better solution but gave up after many hours trying to get the initial setup to work)

2

Set it up as a mqtt sensor.