For doing that, you have to install youtube downloader first.
For the installation use following command:
Step 1: Install python3-pip
sudo apt-get install python3-pip

Step 2: Install youtube downloader using python pip
sudo python3-pip install youtube-dl or you can install by this command too : sudo apt-get install youtube-dl

Step 3: Update youtube-dl
sudo youtube-dl -U

Now you can download by following command:
youtube-dl your-full-youtube-video-url

Advanced Options:
Check all available formats of the video:

youtube-dl -F your-full-youtube-video-url

Download your preferred format :

youtube-dl -f 22 your-full-youtube-video-url

Download a full playlist:
youtube-dl -i -f best ‘’ –yes-playlist