Generally, you cannot include the contents of custom fields in outgoing email alerts and notifications. However with this add-on you now have access to almost all custom fields when creating email alerts or notifications.
In order to use the tags, you would need to know the Awesome Support internal name of the custom field. But, we made it easy for you – you can see all the available template tags, including those for custom fields, by going to the TICKETS->SETTINGS->EMAILS tab and then clicking the HELP link in the upper right side of the screen.
Email template tags for custom fields have the general format {customfield:fieldname}.
Here are some examples of custom field tags (see in the HELP area mentioned above):