Do you know DOS command line where you have to open DOS terminal?
It's the same thing, except when you open you are in a shell.
There are many 'shells'. For the most part they are similar.
Depending on your OS, there are different ways of getting there.
As for me. Fedora. I right-click on the desktop. Open Terminal.
I don't know Yellow Dog (per say) but if it's Linux, it's the same general story.
You will have to know commands such as ls (list), cd (change directory), pwd (print working directory)
--- I'm thinking... there are now easier ways for typically GUI users. How did you initially download Flash?
There are simple ways to install Linux software for many command line challenged
Do you really want to learn command line? Or would you like to learn an easier way to install software?
Write back. And I'll prolly be able to help.