Would like to add a custom font

Hi,

I would like to add Google Font Source Sans Pro in weights: 400,300,700 to my site

I’ve read the following thread: https://kriesi.at/support/topic/new-custom-font/

which advised to : “Insert following code at the bottom of functions.php and then select the font from the dropdown:”

add_filter( 'avf_google_heading_font',  'avia_add_heading_font');
function avia_add_heading_font($fonts)
{
$fonts['Source Sans Pro'] = 'Source Sans Pro:400,300,700';
return $fonts;
}

add_filter( 'avf_google_content_font',  'avia_add_content_font');
function avia_add_content_font($fonts)
{
$fonts['Source Sans Pro'] = 'Source Sans Pro:400,300,700';
return $fonts;
}

I’ve added this filter, uploaded but still can’t see the fonts in Enfold > General Styling > Heading Font or Defines the Font for your body text drop down menus.

Where have I gone wrong?

Thanks.