I know this is probably a noob question, and I have edited

I know this is probably a noob question, and I have edited my thumbnails before. For some reason I am a little slow today and can't remember how to find it. Maybe it is a little more difficult then usual in this theme.
So here it is.... Can someone point me in the best direction to resize my thumbnail images? I would prefer them to be landscape instead of portrait. I want to use the images to post business cards.
The images are in a couple different places.
http://www.gives2.com/blog/item/hayes-auto-sales/

http://www.gives2.com/blog/cat/car-dealers/

I know it is not a wpmudev theme, but hoping I can get a clue from someone.

Thanks for all the help
Richard