Picture Size Issue – Please help!

Hi there, I just bought and installed Highend WP but am having an incredibly difficult time with the picture sizes.

My website is beautyechoesmagazine.com and as you will see all the pictures from each post is stretched and unproportionate. How do I get the pictures to be formatted like this: http://www.naturallylindsey.com/

I really appreciate your help and insight in advance!