It is only available to those testing the new Rules Engine. If you are not on the new Rules Engine and would like to be, you can let QSun know. Here is the link where they offered it:
However, when you go into the App, Click on the pencil in the top right and select edit rules or the Plus sign in the top Left and select add rules. If you used the pencil, click the plus at the top right to add a new rule.
you will see the following screen, last option is location trigger:
