Locate the Youtube video you would like to embed in a text box.
Beneath the video, select Share.
Select Embed. This displays the YouTube video embed code.
Select Copy or use a keyboard shortcut (CTRL + C for PC or COMMAND + C for Mac) to copy the YouTube embed code to your computer's clipboard.
Select Source from the Rich Text Editor toolbar. This displays the HTML code for the text box.
Position the cursor and paste the embed code.
Position your cursor where you would like the video embedded, then paste the YouTube embed code (CTRL-V for PC or COMMAND-V for MAC). The embed code from the video is highlighted for emphasis.
This returns the text box display to normal editing mode. The embedded YouTube video will display as a box marked "iframe." When the item using the text box is posted or saved, it displays the embedded YouTube video.
Select Save to save changes.
The video is embedded in the text box.