I tried edit the CSS into the box. The preview showed up pretty good. But once I press update. It’s reset into the original state again.

Here’s the code:

@import url('https://fonts.googleapis.com/css?family=Athiti|Mitr');

body{
	font-family: 'Athiti', sans-serif;
}
h1,h2,h3,h4,h5,h6,strong,b,#primary-menu a{
	font-family: 'Mitr', sans-serif;
}

PS.Actually all the customize changes were not save. It reset to the original version everytime I go back to dashboard.