Sakuli only supports the active LTS release of Node. For information on what version this currently covers see the Node.js Release Schedule.
In order to be able to run Sakuli on your system, we will assume that you have a working node installation.
To install Node on your system, you can either go to the Node website or you can use tools like Node Version Manager utility to manage various Node versions on a per-user basis. In general, a per-user installation is the preferred way since it runs in an unprivileged mode.