Hi Mary,
Once you hit edit next to the autofill you get this screen...
Select
URL Parameter and then when it asks you for a "parameter name"
You can use whatever you want but it is important to keep this parameter to use in your url. Now when you send someone to that page you will just need to include that
parameter and then a
value. When creating your url:You put ?
in the end of the url. After the ?
you put ParameterName=Value&Parameter2=Value2
& speparates each parameter/value pair.
For example
http://www.yoursite.com/page.html
?Source=Social&Ad=Red