No need to apologize - you are always welcome to ask anything you want to know about the theme.
Ridizain is styled slightly differently than Twenty Fourteen - Ridizain has much wider layout which covers most screens and therefore the background color will be of little use for many users.
However, if you have a wide enough screen and would like to add the options and see how it works out then here are the steps to get it going....
1: First install (unless you are using a child theme) the Functionality plugin. This will create a functions.php file in the plugin directory and a plugin with your site title will appear in the plugins list.
2: Go ahead and activate the new plugin and then click on its edit link to open up the editor.
3: Paste the following code to add support for background color/image to the site.
add_theme_support( 'custom-background', apply_filters( 'ridizain_custom_background_args', array(
'default-color' => 'f5f5f5',
) ) );
Disclaimer: I've not tested this as I do not have a wide enough screen.
Do let me know how that goes and if there's anything else I can help with.