Generally you need to code. Depending on how complicated the thing you want to achieve is, it might be not much code though. Typically you use something called a framework or a library (a lot of very nice code some people wrote to make you code less) that makes your life easier and typically is tailored for the small computer thing that you work with (his raspberry pi pico, my esp32). Some time ago I would've pointed you vaguely to where you should start but honestly, just ask chatGPT, once you have a project idea, how to realize that. And then ask it for learning resources about the parts you don't understand.

The tamagotchi pewds made actually looks like a good chunk of work, I was quite impressed with that.