Browse to fonts.google.com and choose the fonts that you want to use. Depending on the fonts, you can choose different weights and languages too.

Get the import url for your font selections.

Use a CSS editor to create a CSS file.

Add the following code to your CSS file:

@import url('');

Copy the import url for your selected fonts inside the single quotation marks:

@import url('https://fonts.googleapis.com/css?family=Open+Sans:300,300i,400,400i,600,600i,700,700i,800,800i|Roboto&subset=cyrillic,cyrillic-ext');

In the CSS file, apply the fonts to the classes that you want to style. For example, to style the body class you could use:

body {  
font-family: 'Open Sans';  
font-size: 22px;
}

Save your CSS file.

Upload Customized CSS.