How to retrieve RSS from multiple website?

I am a novice when it comes to Bootstrap and css in general. I would like a site with a fixed sidebar, fixed top nav and main content that scrolls.

The navbar is fixed and works ok. The layout of the sidebar and main content is fine too. The problem comes when I set the sidebar to fixed. The main content overlaps the sidebar.

I have tried adding a margin to the left of the main content to push it over but it looks horrible when resized to smaller device.

What is the correct way to achieve a fixed sidebar whilst still maintaining responsiveness?