WYSIWYG = What You See Is What You Get.
- Log into your guide.
- In any content box, click the edit icon at bottom right (under the content). The box editor opens.
- It calls itself “rich text editor” but it's the WYSIWYG!
With a WYSIWYG. you can create HTML using the WYSIWYG's toolbar. You don't need to go into the code.

Of course, if you want to mess with the code, you can. Just click "Source."
Drupal and Guides use the same WYSIWYG ("CKEditor," in case you were wondering).