Newbie: Having trouble creating a full width page

Hi, 
 
Sorry if this is an easy question, but I am a bit confused on how to create a page that is full width when my site layout has a sidebar. I see demo pages that display as full width (ie., the full width demo page), but when I try to use a template to create a new page at full width, I get a sidebar always. What am I missing? 
My theme is Hello and Co. 
Many thanks in advance, 
Gretchen