First, install the plugin using the normal Joomla installer. Once installed, head over to the plugin manager and enable the newly installed plugin.
Next you will need to add the elements to your forms. Either create a new form or open an existing form and you should notice 3 new elements under the Advanced Form Fields header for Country, State and City:
Click on the elements located in the left menu to add items to your form.
There are some combinations of the three elements that can't be used due to how they are dynamically populated based on user selections.
If using these elements, the Country element must always be used. It's not possible to use only the State and/or City elements alone. The proper combinations are:
The fields can be in any order you want. Just keep in mind that the country will need to be selected by the user before the state dropdown populates and the state will need to be selected before the city dropdown populates.
Insert a unique name for the element. Also add a Caption which will display as the label on the front end. You can also add a Description that can be displayed near the field on the front end (location depends on your layout and framework being used).
If you need the fields to be required you can set those options in the popup in the validations tab. Be sure to add an appropriate message that will display when a form is submitted without a selection being made
Save the element once finished and then be sure to save the form.