Configure at Admin Dashboard → Ximenia Theme, then go to Layouts to set the grid widths and allocated positions.
Injected Gantry Gizmos
There are Gizmos that are injected into a site when enabled in the Administrator, and are stacked vertically.
These are the Google Analytics, Page Suffix, Smart Load Images, Typography Shortcodes, Page Class Suffix, RokStyle, Build Title-Spans, Disable Auto Paragraphs, Disable Texturize and IE6 Redirect.
There are times when you just don't want to have your widgets taking up all the room in a horizontal row no matter what the layout. For example you might want to have a widget on the left and a widget on the right, with nothing in the middle.
This is made easy with Gantry with the Force Positions parameter for each layout, allowing you to set the count to a specific row number, such as 4, even if 4 widgets are not published for that row.
Configure at Admin Dashboard → Ximenia Theme → Layouts the varying Mainbody/Sidebar layout possibilities.
Note: If no widgets are assigned to the Sidebar positions, the Mainbody will become full width.
Basic: Using Layouts in Ximenia
To find out about Gantry Layouts and Widget Widths, check out this screencast which covers basic concepts of configuring layout with a combination of widget setting and the Gantry layout control.