To add a text and media area, switch editing on, go to your course’s homepage and click on the + Add an activity or resource button.

This will give you a screen full of options. Click on the Text and media area icon to open the New Text and media area page.

Add some text in the Text field.

Usually text like this is not essential for passing a course, so the Completion conditions would be set to None.

Click on Save and return to course.

If you want to update the text, click on the icon of three vertical dots next to the text and media area and click on Edit settings from the drop-down menu.