When clicking a button, open an animated box

Question

I have some kind of button that has the code:

<a data-scroll class="btn btn-start animated fadeInUpBig" href="">EM QUE POSSO AJUDAR?</a>

I wanted to know how to do when I click on it, open a box from the center of the screen, with scale animation 0% until the 100% for 1 second. And with an X in the upper right corner, in case you want to close, returning to what was before opening the box. (the styling of the CSS box I make later, can be all white even)