The course About page is written in HTML.
To add paragraphs in HTML use this code:
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
The W3Schools tutorials are useful for any and all HTML needs:
https://www.w3schools.com/html/html_paragraphs.asp
Here is a help article from our Knowledge Base (help.appsembler.com) that explains how to edit the About page:
http://help.appsembler.com/article/145-course-summary-page-walkthrough
It includes instructions on how to add YouTube videos. Course Intro Videos are added by the YouTube video ID. If you are unsure, the video ID on a YouTube video is the part that comes after the = sign.