Install the Denver Theme by following these steps:
Log into your eCom back office
Go to Design > Theme Store and do a search for Denver theme
Click on one of the Denver theme variations that show in the results (pictured below). The variations are all a part of the Denver theme, but choosing one will start you off with a preset to quickly begin working from
This preset can be changed after you install the theme.
Warning: If you choose to switch presets after you have made customizations to the Theme Settings page, all of your changes will be reset. Be sure to choose your preset before beginning to make customizations.