Use the Call instruction with the pxStartRunById activity to start an external data flow run that has already been created.
Create an instance of the Activity rule by clicking Records Explorer > Technical > Activity.
In the activity steps, enter the Call pxStartRunById method:
Add the first step:
Method: Page-New
Step page: runOptions
Add the second step:
Method: Call pxStartRunById
Step page: runOptions
In the second step, click the arrow to the left of the Method and specify the runID parameter.
You can find the run ID on the Data Flows landing page.
Click Save.