NextGen – Thumbnails: Resizing & Showing description

Hi
Am using the nextgen plugin to create a gallery. I know this is probably a very simple question but where can I increase the size of the thumbnails? I’ve looked through the various css codes and the thumbnail.php files that are in the plugin but I cant seem to find anything that changes the size.

Also when I preview the page, the descriptions of the images are not showing – if anyone knows how I can fix this, I would appreciate it!!

Thanks
Sam