How to find 'push button in Flow' as the trigger for a BPMN diagram that will be export to MS Flow?

Hi, I created a simple BPMN diagram.  I would like the process to be initiated by pushing a button in MS Flow. I cannot find the trigger when attempting to map the diagram in the Prepare to Export process. I can find the trigger when creating a new workflow in Flow, independent of Visio. Any suggestions? -Rick