You can't. What are you trying to do? Depending on what you are trying to do ycan write variables value during a state transition or perhaps run a dispatch action.
This is for a "Doc Review" workflow which is automatically started when a user saves a files in "Customer Spec" folder.
We have many different people saving customer documents into the vault.
I want the "Doc Review" datacard to pop-up so the user doesn't forget to fill-in.
I have a Template set-up but the user sometimes forgets to run the template.
If you create the file via template you could specify show data card, and the file's data card would show during creation, and before check in. That may be as close as you can get.
If it is a SolidWorks file, as soon as you save it into the vault from within SolidWorks, it should pop up the datacard. The problem with what you are trying to do here, though, is that if you have a file checked in so that you can do a state transition, you can not change any of the values on the datacard.
This is where Joy hits the nail on the head, if you are trying to populate information into the datacard, you can do this with either a transition action in the workflow, or through Dispatch.