How to use the Rich Text Editor (How to write like a word processor)
You can format text, add headings, images, tables, links, and other rich text formatting options if you enable Rich Text Formatting.
To enable Rich Text Formatting, go to "Create Content > Article" (or other content type).
Scroll down to the bottom of the "Body" input area. Below the input area you will see a link "enable rich text. Click on it. You will se a word-processor like interface, which many people will find more intuitive and easier to use.
In order to learn how to use each of the features, you have to experiment with each one of them. But most of the features are pretty much intuitive. In order to format bold text, highlight the text and click the button "B". Duh.
Some features are more complicated. But it's not rocket science, just try it and you will figure out how they work.