Changing the 3 Column Layout Margin Width

Hi,

I’d like to use the 3 column layout for a page on my site. The page is a members page that is dynamically created for each members profile. For this part of my website the 3 column layout is needed but I noticed that there’s quite a bit of white space on the sides of my page yet the center column is a little too narrow for me. So my inquiries are:

How can I make that center column wider?
Do I need to adjust the size of the 2 sidebars for that page template as well?
Can I add some custom css to accomplish this or will I need to edit the template files?

I’ve included a pic (filesystem:chrome-extension://fdpohaocaechififmbbbbbknoalclacl/temporary/screencapture-www-coupleskink-com-members-setting-upgrade_account.png) of the page I’m referrring to since the site is still in maintenance mode…the address is http://www.coupleskink.com