Changing width of center text column

OK I am almost done getting my blog to look like I want it to. Nothing fancy, but atahualpa makes it look elegant enough

I have removed the left sidebar, and would like to get the post text in the center column to be more compact without changing the width of the right sidebar or the entire layout. I would appreciate if I could be pointed to how to do so two ways:

* By increasing the white space to the right of the text in the center column (about an inch of white space.)

* By adding white space to the left of the right sidebar, inside the dashed border.



Sorry if this is a really basic request, but I tried fiddling with all possible options, with no luck, and I know nothing about HTML or PHP. It's like I am throwing crap to the wall and seeing what sticks

Thanks much.