On mobile devices you may notice a download button directly on the video or you can download apps that download. When using a desktop you will need to use a third party website. Most sites just require the link to be copied and pasted on to their site and will provide a download link directly. Here are few sites to try:
YouTube Downloader HD: https://www.youtubedownloaderhd.com/
WinX YouTube Downloader: https://www.winxdvd.com/youtube-downloader/?__c=1
4K Video Downloader: https://www.4kdownload.com/products/product-videodownloader
Please be advised it is against You Tube Terms of Service to download videos protected by copyright. This article gives instruction on how to download You Tube videos that do not violate those terms. There are 2 types of videos you are free to download from YouTube:
PUBLIC DOMAIN VIDEOS
Videos that are considered public domain are not protected under copyright or the existing copyright has expired. These videos can be download and editing for personal and commercial use. For more on public domain read on its classification on the Creative Commons website by CLICKING HERE.
Creative Commons licenses grant the right to reuse the content under certain conditions. In some cases it is restricted to personal use only, sometimes requiring attribution to the original author and in other cases requiring you to share the edited content as creative commons as well such as a Share A like License. For extra safety, contact the original creator when possible to verify licenses and permissions.
Videos on YouTube are uploaded with either the Standard License (Work protected under copyright) or a Creative Commons by Attribution 3.0 License. The CC by 3.0 License grants the rights to use the video for commercial or personal use. You can use the content as is, or edit, modify or build upon the original work. These videos require attribution to the original author as well as noting if the original work has been changed or edited. You must also include the type of license and a link to that license.
An example of an Attribution might be:
This video has been edited from its original version. Original Video: (Video Title) (Link to Original Video) Licensed under Creative Commons By 3.0 Unported. https://creativecommons.org/licenses/by/3.0/
To learn more about the types of licenses and their restrictions check out the Creative Commons website by CLICKING HERE.