Help with integrating DIY wakeuplight into HA

Hi all,

I’m currently working on a DIY wakeuplight based on an esp8266, it’s a fully custom design with custom code.
I’d like to use HA as its user interface, therefor I need a card that allows me to configure the esp8266 via MQTT.
I’ve found some examples on this site but am struggling with understanding how to get the data entered into the card send over MQTT to the esp8266.

The example above also uses HA automation to trigger an alarm, this is way out of my scope, the esp is fully self contained, I only need to send alarm time and which days the alarm should activate.
The actual alarm functionality is covered by the esp.

For me it doesn’t matter if it’s send formatted as JSON or whatever, I can rewrite to esp side MQTT parser to whatever is needed.

Can someone provide an example on how I can achieve this?
Any help will be greatly appreciated.

Many thanks!