Newsletter subscribtion HTML CSS JS

Dear people,
I am working with Blogger and I am a beginner. I want to add this newsletter subscription to my website: https://codepen.io/ainalem/pen/ZxbbwO
But I can only add the HTML and CSS code, not JS. And after I have done that, when I enter an email address and press enter, it refreshes the page. Do I have to change something in the HTML/CSS/JS text? Thank you very much in advance.

Also in #HTML _↴