The toolkit must be installed and then loaded to be used.
It can be installed in GNU Octave directly from the website, or can be installed in an off-line mode via a downloaded tarball.
The toolkit has a dependency on the netcdf library (https://www.unidata.ucar.edu/software/netcdf/), so it must be installed in order to successfully install the toolkit.
The toolkit must be then be loaded once per each GNU Octave session in order to use its functionality.
With an internet connection available, the package can be installed from octave-forge using the following command within GNU Octave:
pkg install -forge netcdf
The latest released version of the toolkit will be downloaded and installed.
With the toolkit package already downloaded, and in the current directory when running GNU Octave, the package can be installed using the following command within GNU Octave:
pkg install netcdf-1.0.18.tar.gz
Regardless of the method of installing the toolkit, in order to use its functions, the toolkit must be loaded using the pkg load command:
pkg load netcdf
The toolkit must be loaded on each GNU Octave session.