I would like to install PuTTY in Qubes.
In Template, I type
sudo add-apt-repository universe
sudo apt-get update
sudo apt-get install PuTTY
It does not add repository and does not install PuTTY.
If you can install PuTTY yourself and let me know it can be done and commands used, please post. Or at least post mistake i make.
If you are on a debian-based template all you need to do is:
sudo apt install putty
Kind regards another Qube N00b 
Other Qube N00b is correct.
The qubes did not like way I type PuTTY
It likes putty but not PuTTY
I spent 7 hours of troubleshooting before figuring this out with your widsom of the qubes.
That’s why I use synaptic in debian based distros, to easier browse packages.