Right way to set environmental variables and how to update it while publishing apps

Hey, I’m coming from a web development background and I’m new to mobile app development. One of my main concern is, how I’d set up env variables in expo and how and where I’d set it up when I publish my app. Excuse me if my qns is dumb but I’d really appreciate if anybody could. Any blog, videos etc would also work.

Thanks in advance!

Anybody?