Here’s the simplest way to enable SSH Remote login with Putty to your Ubuntu Linux server.
In your Ubuntu Linux server:
sudo apt-get update sudo apt-get install openssh-server sudo ufw allow 22
the first line tells linux to update package
the 2nd line tells Linux to install openssh-server
the 3rd line tells linux firewall to allow access to port 22 (used by Putty).
Now you should be able to remote login to your Ubuntu Linux server by using Putty.