Click on Website from the drop down menu on the left hand side of the page.
From here click the Design dropdown menu and Click Themes
Click Edit on the website you want to change page types for
From here click Page Types
Click the page type you want to add content to e.g. 2 Column
Here you can Add Content to your desired side, any content you add here will now be placed on new 2 Column pages you now create. Note: You can click to have all 2 Column pages updated with the content added.