Hi @kris-a559, I'm happy to help
First, you'll want to use "Row Added or Deleted" as the automation trigger, since you wish to overwrite data in the row that was just added:
Then you would select the action "Overwrite" to specify which column you'd like to update (in your case the Case Owner). In that action, you would click Run Options to specify to only run if the Source data in that row is an "email". Below this, you can use your FINDROW formula to specify the user you wish to assign as the case owner:
In regards to your FINDROW() formula, it will return the first user in the table that meets that criteria. If you'd like to specify further, you can use the AND operator to add more criteria.
You can also use automations in-app by adding them to buttons. Depending on how your app looks and your goals, that could be another option.
Hope this helps! Let us know if you have any further questions.