Go to WP Menu => Appearance => Customize => Click on Widgets
You can see here the option to add widgets click it and add the widgets you like
Go to WP Menu => Appearance => Customize => Click on Footer
You can see there is option of above header click it 
Go to WP Menu => Appearance => Customize => Click on Footer
You can change the background color, background image , opacity color and opacity here.
WordPress Dashboard > Appearance > click on widgets
