Thanks for keeping in touch! When running this step template on its own, it doesn’t actually deploy the package. If you had a package step that deployed the package, this step template running afterwards in the same process should then pick up this script file from that previously deployed package.
I’ve seen it accomplished (having the script in a package run directly from the step template, outside of the deployment process) in another way by instead referencing the package (by uploading and extracting) and executing the PowerShell script from an inline PS script in the step template. Something like the below:
Would that give you the behavior you’re after? Let me know how you go or if you have any further questions going forward.