Need WP Post pictures bigger

I am having a dilemma. Okay, I need my post pictures bigger on my site. You can look below at a sample post to see what I mean:
http://amazingpicturesonline.com/pictures/a-real-cup-of-coffee/

I am only using a FEATURED image. (No pic inside the post) and that featured image also acts as a post..

I want the pic inside the post to be the same size as the image on the front page (400x400)

If anyone can do this let me know. I can pay after once the job has been completed. Let me know how much you need for this job.

Thanks

dude, i think the image now is OK, at least in my eye, but if u want larger image u can find some plugin, someone shared b4

btw, could you tell me what theme you use ? so pretty

and little problem when use Chrome to view your site

Hey op i can increase the size of Pic in the post add me on skype : floralchamp

Thanks
Neo

please add me on skype.i can do this