If you want to edit the link that appears in cPanel(Video Tutorials):
Links to our video tutorials are embedded in a few places in the product but all link to one point.
You can edit the /usr/local/cpanel/base/frontend/x3/tutorial.html file specifically:
<frame name="mainFrame" src="https://www.cpanel.net/products/cPanelandWHM/linux/cpanel11/tutorials.html">
and use whatever url you want.
If you don't want to use an iFrame but instead redirect I recommend reading this StackOverflow answer: How to redirect from an HTML page? - Stack Overflow
If you want to edit the link in the getting started popup this file contains the link:
The link is also located in these locations: