To add custom font follow the steps 

Step 1) add to parameter  wp-confog via cPanel

add this line: 
define('ALLOW_UNFILTERED_UPLOADS', true);

Step 2) add the PHP script to the function file 

// allow otf file upload to media library
add_filter('upload_mimes', 'azedw_custom_upload_mimes');
function azedw_custom_upload_mimes ( $existing_mimes=array() ) {
    // add your extension to the array
    $existing_mimes['otf'] = 'application/otf';
    $existing_mimes['ttf'] = 'application/ttf';
    $existing_mimes['eot'] = 'application/eot';
    $existing_mimes['woff'] = 'application/woff';
    
    return $existing_mimes;
}

Step 3) add Font to Theme Option 

now you can use this font to change your elements via CSS

example of change HTML element via CSS: