Width of sidebar and content area

First of all, Upfront themes are awesome! And I'm having fun using theme. I need help customizing them though. If you open gmail on your desktop there's very little space between the sidebar and the content area. and the width of the sidebar is pretty small. I want to know
1.How to achieve the same result usIng fixer and other upfront themes.
2.How to change the width in other WP Themes generally, what properties will I likely need to edit and how. I am using localhost, I understand that your answer cannot be that specific. Thank you