Workflow mass update records

I’ve reading through all resources here, but don’t find an example how to mass update records using Workflow.
I manage to process a workflow On Saving a record, but how to process a Workflow on multiple records in 1 move?

Let’s say I like to change Postal Code on all my Leads from 1000 to 2000.
In the creation of the Workflow I can choose Run on all records, but what with Run? Select here Always? (I found no info on this criteria)
What about Repeated runs? Need to check that? Is it needed when working on multiple records?

Condition; Leads - PostalCode - Equal to - Value - 1000
Action: Modify Record - Leads - Postalcode - Value -2000
then Save, and now when or how is this workflow going to get executed?
Scheduler is active (every hour>workflow), crontab OK, but I don’t get any action?
What am I missing here?