height of website pages

Hello,
I’m using this theme (dazzling) on my website, but I have a question:

When a page has little content, footer adjusts as this content. For example: a page without content, the footer appears almost in the middle of the screen.

How to make the page height always stay at 100% of the screen? even if the rest of the page is empty.
Could someone help me?

Thanks in advance!