Thank you for writing in, 1) on your Slider Settings, please set the Slider Layout to Auto
2) On the Page Settings, please set your Slider in the Slider Settings: Below Masthead option.
That should put your Slider below the header and take the width of your Main Container (Content + Sidebar)
There is no way to put the slider in the Content and make that extend to the Sidebar. You can set the Slider Layout to Full-Width but that will take the entire width of the screen.
Hope it helps,