InfoPath Dev

I'm trying to use several InfoPath 2007 forms in one document library. I have been successful in setting that up, by using Manage Content Type within a document library. All the forms have several fields that are named exactly the same. What I want is for the information in the identically named fields to auto-populate into the SharePoint columns within the document library. I thought I saw an option somewhere that would enable me to do this, but for my life, cannot remember where. Could anyone give me a hand with this?

Thank you.

When you are publishing your forms as content types, you promote the properties from the first form and then they are available as columns to select from for other forms that are content types. The column should be available under the Site column group drop down - I'm attaching a screenshot.