YouTube videos are creative works that are protected by copyright.
Your use of these videos for instructional purposes may qualify as fair use, but it's often not black or white. The US Copyright Office describes the factors that come into play when considering a fair use argument:https://www.copyright.gov/fair-use/more-info.html
There is another issue here that you have not mentioned. When you use YouTube, you agree to their Terms of Service. The Terms say, in part, "You may access Content for your information and personal use solely as intended through the provided functionality of the Service and as permitted under these Terms of Service. ... You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. "