JS React path

I am very new to web-development, so excuse me if I am wrong. I learned Flask first and I created an entire platform with it. I used Flask for back-end, HTML&CSS for front-end and SQLite for database. I wanted to learn JS to create cool animations, transitions and add more interactivity.

I have almost completed the path ‘Create front-end applications with React’ but I see no styling lessons what’s so ever. It is all about components and rendering them. This, essentially, operates just like Flask render_template.

My question is: How do I add style and interactivity with React? I just do not understand why JS is admired for its simplicity and interactivity. I am definitely missing something… If someone could suggest where to learn styling an existing platform with JS it would be very much appreciated!