Creating homepage with category columns

I’ve been trying to do something like this too. I went to appearance/theme options/layout. It says that you can enter your custom CSS but it doesn’t seem to change anything. I wanted to have 4 columns – 2 sidebars widgets on the outer edges with 2 columns of content in the middle. It only allows for 4 columns of posts. Maybe my CSS coded is messed up?

#sidebar-left .widget,{
float: left;
width: 220px;
}

#content .twocol{
float: left;
width: 440px;
}

#sidebar-right.widget,{
float: left;
width: 220px;
}