After you have the theme installed you will have a dashboard page where you can options for your site. You can choose from a number of overlay opacities for the background image. You can also choose to set the maximum width of the content container. Whatever you set here the css will limit the width to a maximum of 50% of your window width. This setting just limits the maximum width. This will be overridden to fit on mobile devices where the width scales up to 100%.
Set your autonav block for the main area to display all the pages all the time. They will only show on mobile devices. Set the Secondary Nav area to include an autonav block and set the options to display the second level with no subpages shown. This will give you second level navigation. The mobile navigation menu will activate automatically. Choose "None" from the autonav templates if necessary.
Pro Blog styling is included however it is not necessary for the functioning of this theme. You can purchase a licence here: https://www.concrete5.org/marketplace/addons/problog/ Use the default Pro Blog settings and you will have a display set by the theme. If you choose a custom template it will override the theme settings.
In the Pro Blog dashboard set the thumbnail image size to the maximum you've chosen in the Intrinsic dashboard page for best results.
While logged in choose the Edit > Page Properties. Under the Custom Attributes choose "Background Image". Select an image from your file manager and save the changes. After you refresh the page the image will appear if your cache is turned off. If you have issues with this clear your cache in the dashboard and try again.