saving Advanced form to table

I've looked through all the video tutorials, but there is no clear step-by-step on saving form data to a table. I've placed the "Save Data" action on the end page, but when I go to properties and select the SourceTable drop down it is blank. What do I need to do to populate that table?
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I tried adding External Table, but no joy there either.
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Instead of referring me to the videos or telling me something is coming soon, can you please answer this question?

Bumping for visibility - I really need to figure out why SourceTable isn't populating. This is an Advanced Form.