'Magazeen' Theme Image Problems

If anyone can help me that would be fantastic.

I am using the free ‘Magazeen’ theme on my blog (https://www.thefighthouse.x10.mx/) which I am still designing and I have an issue:

If you see the top post entitled “Blog: Test”, you’ll see the top image (of two guys). If you click that image, you are taken the ‘single post’ version of the post. Now, I would like to decide where the thumbnail is cropped, but I am unable to do so. It is not as simple as cropping it in the image editor. Does anyone know how I can control this? I know the site is using something called timthumb.php to automatically process the thumbnails, but it is quite irritating.

Thanks to anyone who helps in any way! ??