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By default, S4S will use an ID of "A7F779B9-5FCF-45CC-866B-7C973F5C4FAC", but if your install is different, this will need to be configures in the S4SMapping.config file. Otherwise it is not necessary to configure this value.
First find the '/sitecore/templates/Web Forms for Marketers/Form/Submit/Save Actions' item and retrieve its Sitecore Item ID:
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