I see some linux page says how to install the key:
wget http://packages.ros.org/ros.key -O - | sudo apt-key add -
What is "-O -" in wget?
It seems related with "add -".
How these works?
I've been searching the internet about wget, and found many posts on how to use wget to log into a site that has a login page.
The site uses https, and the form fields the login page looks for is "userid" and "password". I've verified this by checking the Network tool in Chrome when you hit F12.