How to add a custom dialog in Simphony 2.9?

Hi

Where is the document to walk through how to add a custom dialog in Simphony 2.9?

Example 1:

In the employee log in screen, we would like to add a custom dialog for password and couple additional options. How can we do that?

Example 2:

When a button is clicked, we would like to open a custom dialog that invokes an external service, so the dialog will display some data retrieved from that service. The data are completely outside of EMC. How can I do that?

Thanks