How to add and style search box

Hello wpmudev team, I am trying to make a search page and I want to have the whole page background color to be: #3893b5. It should look something like this:

OR like this:

The problem I have is I want the page to be the height of the browser screen, and I want the the search box to be centered vertically. I know how to center vertically but I don’t know how to make the background height the same as the screen height. I would also like to apply some animations like the ones above, but most of them have scss:

How do I add SCSS? And how do I add a search form without using widgets?

My page is here: