Change Font Size in…Title? Tag? Not sure!

Okay – I think I’m not finding the answer because I’m not looking for the right ‘section’. If you go to the link – the top area where it lists the page name, and under it has the path to that page…for the site I posted, it would be Contact Us in the blue section. I’ve searched for adjusting the font size for the page title and tab, but not found anything that works – am I calling it by the wrong name? I just need to reduce the size of what shows on this page as Contact Us in white font – other pages it’s way too large. I’ve tried using CSS code:

.site-title {
font-size: 50px;
}

Changing the size down to 10, just to see if it works – it doesn’t, which is why I’m thinking I’m in the wrong area? Obviously, coding is not my strong point!

The page I need help with: [log in to see the link]