Hi newbie Tabs, I'm kinda new too, but I know that the heating cores job is to conduct heat to the center of a large or deep cake pan. You if you use the one like the photo Ladycake posted you prepare it just like you do your baking pan, including the inside, then put it in the center of the cake with batter inside the core. When the cake is done you remove the core, use the cake baked inside it to "plug" the hole in your cake, use some icing, etc., to "glue" it in the hole, and then ice your cake as you normall would.
It has been posted here in the forum that you can use icing nails as a substitute, so I guess if you had baking potato "nails" you could use those too.
I used one just this week, and without it, I more than likely would have had a cake disaster with a seriously underbaked cake, but I think the core saved it!
Hope this helps. Janice