content area and sidebar: How to change size and location?

I moved my sidebar to the right. Now I would like to increase the size of the content area. I would also like to lower both and add a widget above both. Is this possible? I did try a few solutions I found on here but I think maybe it didn’t work because I moved the sidebar? I just barely started but you can see what I am talking about at http://www.thebridalgownblog.com Thanks!