Please referto my previous article to learn more about SharePoint Designer 2013 Workflows.
Description:
This condition is initially displayed in a workflow step as if created by specific person. Use this condition to discover whether an item was created by a specified user. You can specify the user either by entering their user name or email address manually or by selecting the user from among users already listed in SharePoint, Exchange, or Active Directory.
Example:
In this example, I will check if the current item is created by a specific user (Vijai Anand Ramalingam), if the condition is satisfied then the current item “Notes” field is updated with string value “Condition Satisfied: Item created by Vijai.” .
Workflow Design:
Result: