You can insert iframes from YouTube or other sites into your Pages website. Here's how:
- Click the link to "Disable rich-text" located below the Body section of the page you are editing (see image)
- Copy the iframe source code from the site where the content is being generated. For instance, Google Calendar (under "calendar settings") and YouTube (under "share") both make iframe code available.
- Paste the iframe code into the page (with rich text disabled).
- Save the page.