It's OK now.
You move stuff on that (or most any) page by opening the template file for that page (in this case, tpl_product_info_display.php) and looking for the code that controls the part you want to move.
The developers have made it easy in this case by enclosing the code in comments that identify the page element the code applies to, as BOF (beginning of file) and EOF (end of file).
So, to move the Add to Cart section, look for all the code between <!--bof Add to Cart Box --> and <!--eof Add to Cart Box -->, Cut it (including the bof and eof comments) , then Paste it where in the file you want it relative to the other elements. In this case, probably just before the Product description section.
In any case, there's a certain amount of trial-and-error involved, and it's likely you'll have to go into the stylesheet and fiddle with padding and margins to get everything lined up the way you want it.