How Can I Make My Sidebar To Have White Background Instead Of Plain Background Display Inside?

Have been finding it cumbersome to add white background inside the sidebar of the widget under my post like ogbongeblog …as seen below

See this :

Sir, I didn.t mean to add space to it. I meant to add WHITE BACKGROUND inside the sidebar instead of plain as illustrated above. (see where the arrow indicate) sir.

Sir, I’m waiting for your response