In the Workflow Designer in Sharepoint Designer, you'd add an action to email a user. The user part should be a clickable hyperlink that when clicked will open a dialog box. In that dialog, you can specify List lookup and point it to the person/group field.

In the Workflow Designer in Sharepoint Designer, you'd add an action to email a user. The user part should be a clickable hyperlink that when clicked will open a dialog box. In that dialog, you can specify List lookup and point it to the person/group field.

You might have to look closely at the fields, because the Created By field has an internal field name of Author. So your field might be Author1 or something like that.