Where can I find the Screencast-o-matic tool in the Rich Content Editor?

You will find the ScreenPal tool in the "Apps" list in the Canvas rich content editor.

  

 

When you click the "Apps" icon, you will find ScreenPal in the drop-down list.

Click ScreenPal to launch the tool.

 

A window displays your current ScreenPal videos which you can embed.  You can also choose to launch a new recording or to launch the video editor from here.