On Ubuntu box needed to install openssh-server:
sudo apt-get install openssh-server
And net-tools also did not come pre-installed:
sudo apt install net-tools
Once that is in place, check the IP address like so:
On the Windos laptop I already had Putty installed.
Just to be sure, I added some security measures, following this guide.
The secret key I generated on the client (windows laptop) using Puttygen as explained here https://www.u.tsukuba.ac.jp/en-puttygen-keypair/.
Next step will be to configure the firewall for external access.