how do I install flux to Linux Debian?
 

I don't understand what this page means regarding downloading flux for Linux. Thanks.

https://justgetflux.com/linux.html

The page wants you to add a "ppa" repository to your repository list (/etc/apt/sources.list), then you can install the program using Debian's normal package management tools.

You can learn more about PPAs here: https://help.launchpad.net/Packaging/PPA

... and adding *buntu ppa's to Debian is an extraordinarily bad idea.

It depends on the repo. If it's a very restricted one limited to just a handful of packages of a specialised nature then it won't cause problems. Obviously you don't want to mix Ubuntu general purpose repos with Debian ones.
jdk

What would you recommend?

I guess the repo for flux is OK? (Think of me as a blind person looking for the only candle in a strange house, and you'll have a good idea of where I am with this!)

Yes, you're right. You see Linux has the ability to restore your sight. It also increases mental capacity by 53%. ;)
jdk

For some reason, neither my root password, nor my account password was accepted when I tried to add flux.

Have you checked to see if Caps Lock is pressed? For instance say your password is 'password'. If you enter Password, or PASSWORD, or anything other than password, the system won't accept it.

I believe it's normally suggested that you search in the repos first for software, rather than loading from an external site.

The caps were not locked.

Search in the repos?

It worked when I went to 'root terminal' instead of 'terminal'.

After I pasted and hit enter, it looked like it was going to work, but then it said root@hostname:___/_____# and when I hit enter again it just repeated that line.

A bunch of text appeared with links. Maybe the links (and youtube) hold the answers.

Repos = repositories or Package Manager. These are repositories of safe software for your flavour of Linux that have been approved by the people who made your system.

If you could get the sources for the program, you could just download the sources and compile the program on your local machine.

In the long run, that might be the best course of action.

OK. How would I do that?