How do I make my Workflow into a pop up overlay?

In the Library screen of the Workflow section of MyMalcolm click the three dots on the right hand side of the screen and select "Embed"

This will take you into the Share section of MyMalcolm! Here you can choose the type of embed you want to create.

Choose "Overlay" and work through the screens - the Workflow you came from will be preselected as the content you want to surface in your Overlay. You will be offered various styling and display options and at the end of the process you will be supplied with the code that you should add to your webpage HTML and the inline code used to launch the overlay.