This method can be used for any font hosted externally.  However if the font is hosted on another domain, the following header needs to be set on that domain:

Access-Control-Allow-Origin

Embedding on a Landing Page

Include the Font

Paste the <link> into the page properties script tag:

<link href='https://fonts.googleapis.com/css?family=Roboto' rel='stylesheet' type='text/css'>

Use the Font

Add styles to the pages Custom CSS section to specify where you want to use the font:

Embed in an email

To embed in an email, you will need to use an import statement:

Embed in a brand

A font can be embedded into a brand and used anywhere the brand is used:

If you want to use the Google font for your forms as well, add this section of code to Custom CSS block:

If you are embedding the font in your brand, you should also put the link statement into your global script tag under Administration => Account Settings:

CSS example

Note that this CSS will vary depending on how you want to apply the font. The sample CSS below will apply to all elements of the page:

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

body,
body *,
body .activedemand-button-container .activedemand-button, 
body h1, body h2, body h3, body h4, body h5, body h6,
body p, body li, body label, body input, body textarea, body button {
  font-family: 'Roboto', sans-serif !important;
}