I'm not too familiar with slack; but I have a couple of suggestions that may help you in general...
See if you have 'mc' installed. (midnight commander, a file & directory manager that has an editor in it.)
My personal feelings are that we newbies HAVE to be masochistic to use vi!
In all instances do not type the quotes when actually entering the commands. (without the quotes)
At the command line type 'mc',if mc comes up you will find it useful to set some configs;
'F9', 'options', 'configuration'; 'Alt-d', mark all boxes in 'Other Options', 'Alt-s.' Now the 'right-left-arrow' will take you in and out of directories on the tree. When you have the file focused/hi-lited you want to edit, 'F4' brings up the editor. (cool-edit)
Another little tip; typing 'whereis mc' should tell you if there is a presence.
Ever get 'writer's block', your mind goes blank and you can't think of the command you need to use? Try tapping the 'tab' a couple of times!
The program/script/command 'dmesg' runs during boot and gives us a log of most of what transpires during the initial boot process. From the command line just enter 'dmesg' (without the quotes) and it should fill your screen. (use 'shift'-'pageup'/'pagedown' to scroll back & forth)
In case you don't have 'mc' (YET!!!) see if you have 'nano', a small editor that is user friendly.
Looks like you are coming along just fine... hang in there and before long you'll have the hang of it.
The BEST thing I've learned about linux... don't matter what distro, there is most always light at the end of the tunnel... what you learn as you go along you can use always... where-as with Brand-X WinDOS there is just tunnel and MORE TUNNEL! (If you COULD, it would be illegal to fix a bug in THEIR operating system.)