List Appearance Settings
This page can be accessed by going to System > Settings > Appearance
Template : If you have installed and enabled additional templates, select a Storefront template to edit it's settings.
Storefront Site Width : Set the width of storefront. Example: 100% or 1000px.
Storefront Site Width setting is optional not all templates allow this setting to work. Please contact your template developer if this setting is not work for your template.
Default storefront theme
In order to set installed template as default theme for your Storefront go to Design > Templates page and click button.