Your mini came with a Mini DVI to DVI adapter. In order to use two VGA monitors with the mini, you'll need a [Mini DVI to VGA adapter|http://store.apple.com/us/product/M9320G/A] and a [Mini DisplayPort to VGA adapter|http://store.apple.com/us/product/MB572Z/A], available online, at any Apple Store, or many other places.
Once you have the adapters, simply plug your VGA monitors into the mini, which will recognize them and configure itself automatically.
Shawn