Thumnnails issue

Thumnbnails are not showing correctly. how to make thumbnail in correct proportional.Thumbnail is showing big image. how to make thumbnail resisze
is there any option for that like you given for big image. How can we make thumanil 100* 100 px. How me the code how to do it. i tried alot bi\ut not getting. please help me. only one big imagr is showing in thumnbail. I want thumbnail like showing in your plugin screenshot. how van i make that.

http://wordpress.org/plugins/wp-ad-gallery/