To install the YouTube add-on, start off on your Kodi home screen. Kodi comes with the official repository installed by default, so it's quick and simple to install an officially supported add-on like YouTube. It also means you don't have to go through the hassle of adding a new repository to your Kodi installation. This means that you know the add-on is legal and that the Kodi development team has agreed that it's safe to use.
Installing the YouTube add-on for Kodi is very easy as it is hosted in the official Kodi repository.