How to assign a new layout to your categories?
Category pages are dynamic pages created by wordpress.
You can assign a global layout to all categories or to specific categories within the theme panel under the Archives Settings.
Global Settings - http://d.pr/i/19DPR
Individual Settings - http://d.pr/i/180N8
From there, you can assign a layout, activate a sidebar and many other adjustments.
The same applies to Search Results, Tag Results & Author Posts