Ahh...getting frustrated. I need blogger help please!

Okay, I'm finally setting up a blog for my kids with the idea that I'll use it as a journal for them and then print into a book.  I just did my first post so this is very new to me and I'm just figuring things out.  I have it aligned left and I set the picture size as "extra large" but they are all cut off now because of the stuff on the right side of the screen like archive and posts.  Please tell me how to fix this.  I want it to be big pictures, text aligned left (which I did) and I don't want the pictures to be cut off.  Thanks!