When a client's Padot instance has Salesforce User Sync already enabled. That allowed us to create the Pardot user from within Salesforce. 

  1. Navigate to the Setup > Users > Users section of Salesforce
  2. Click on the target user
  3. Assign the Pardot permission set
  4. Navigate to Setup > Pardot > Pardot Account Setup section of Salesforce
  5. Click Edit User Assignments
  6. Add the target user as a Marketing user
  7. Save
  8. Wait about 10 minutes for the user to sync to Pardot