How to change 'Template' in 'Product Pages'

The plug in I'm having trouble with is not the Dashboard - There is no MarketPress selection offered for me.

My issue is in MarketPress.
When I create a product page it shows the 'default' page view. I would like to change that view to be 'Full width'. I am using BlogsMU theme. How do I do get my checkout pages to show a full page view. Thanks!