[Jack-Devel] help for linux virgin

Hello!  As a person who only knows for sure that sound goes in the ear, I am a linux (mint 18.1) virgin and a sound noob.  In trying to figure out how to record more than one line at a time I am arriving at JACK, only to find it is apparently either member only or invitation only website.  Not knowing the protocol here,  I am asking:1.  How can I get invited/allowed to get JACK to try and learn what all it can do to/for me?2.  If I can get the invitation, I need to know how to physically install it as nothing like JACK is in the mint software manager unless one counts the 12 or so things that appear to be addins to JACK.  There is no actual installer that I see which makes complete sense if this is a somewhat restricted software.3.  Can you inform me of what software will best handle more than one line in?  Audacity, which is all I have ever used I thought powerful until I realize it will handle only one input. As background last night I did get some of the things off the repository of mint like QJackCtL, and Jack Rack.  What I saw was that QJackCtlL turns off any sound that is being played/recorded the instant I selected any button on the window.  Not a great start.   I will and do appreciate whatever help I receive from you and Thank you in advance.Richard Clary