From within the DTS package editor: Package, Properties. Second tab is Global Variable.
You'll then want to insert towards the beginning of your workflow (or wherever appropriate) a Dynamics property task, so that you can "plug your Global Variable" into various spots in your package, meaning - actually use the variable..
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?