To create source tracking URLs, you can manually build them by including any or all of the three variables available along with their values in the URL, as in this example:
www.yoursite.org/?utm_campaign=endofyrdonation&utm_source=fallnewsletter&utm_medium=email
Once you build your URL, you can disseminate it over the appropriate channel and inbound visitors using that link will have these variables associated with any action they take while they are on your website for the duration of their session.
If you prefer, you can also use the URL builder that Google has. You may elect to add additional variables through Google's URL builder but only the three variables that Soapbox works with will be saved to Salesforce or Microsoft Dynamics when a visitor takes action on your site.