How do I change the layout?

I really want to change the layout of the articles by making the main body of the article narrower and also to have blocks on the right hand side to show related article, etc.

Please tell me how I can go about to do this. Take look at this predefined article as a sample of now and where I want to do be per my description above.

https://www.mybooks.solutions/by-the-numbers-blog/quickbooks-online-tutorial-setting-up-recurring-transactions