Changing Width of Site/Page

Hello!

The main homepage of our site (www.globalcenturion) has 6 linked boxes. These used to display in 2 rows x 3 columns. A new update to the theme forced it to move into 3 rows x 2 columns. Besides making the boxes smaller to fit, is there a way to increase the width of the page?

Any guidance would be appreciated.

Thank you!