Struggling with project. Controlling home assistant through Rest Api

Hello everyone,

I’m working on a project to use LVGL UI’s generated with the help of Squareline Studio on Esp32 display devboards (like CYD, Crowpanel, Sunton).
I’m trying to achieve similar results to what is seen in this video:
https://youtu.be/pMRXa-KXbbw?si=msORWnalLCFWgE3c

So far I’ve been able to create a UI with several imagebuttons, as well as add wifi to the .ino file and upload sketch, confirming the UI loads and the device is seen on my network. If the user that created teh video would upload his code, I’d have no trouble making this work, but he doesn’t. I’ve tried reaching out 3 times as well.
Where I’m having trouble is adding Rest API to the files, creating a set_entity_state and get_entity_state function, so that I’ll be able to see devices states and toggle them using the buttons in my UI.

This is a project I’ve been working on since August, with no luck with what I’ve mentioned. I’ve been absolutely dying to make my squareline studio GUI’s useful with my HA setup. What’s unclear to me is where exactly I should add the functions described in the youtube video.

If you have a moment and could watch a section of this video and elaborate - even a little - I’d be eternally grateful.

Another thing, in the video the creator mentions abandoning MQTT in favor of HTTP requests. If I could even find clarification on how i could use even MQTT to accomplish my goal, that’d be amazing.

Thank You for your time
-Gabriel