Dynamic page for input text by vanilla JS or JQUERY?

I am building a CRUD blog app. And on the part of creating a post, I faced a problem. I wanna make a dynamic page when you input the text, upload IMG, and so on. As shown an example https://telegra.ph/

But, unfortunately, I don't know any front-end frameworks and I can only make a form like this

Maybe someone could help me to make a dynamic page by Jquery or vanilla js like Tgraph. P.S Backend Jinja 2 Python.