Change Homepage Layout

Hello, I am going into the second year with my class website. With two weeks to go before class starts, I am making some changes to my site. One change I am considering is changing the default layout from the current (content-sidebar) to three sections (sidebar-content-sidebar). I would want this change to apply ONLY to the homepage.

Ok, so I went into genesis layout extras and changed homepage layout to “sidebar-content-sidebar.” Now my homepage looks like:

https://www.blackboarddreams.com

How do I adjust the width of the sidebars and the content section? Thank you for your help…

Sean