How can I install plank or docky?
Your best bet is to compile them from source, and install them in to /usr/local.
How? (I am a linux noob).
Both plank and docky replace significant parts of Gnome and I wouldn’t go that route, unless you’re using some really basic desktop environment instead (but, you didn’t tell us that).
I would if I were you install the dash to panel Gnome Extension. It’s a really nice and simple panel where you can pin favorite apps. It integrates really well into the default desktop and I think it’ll meet your needs. And you won’t need to install software manually 
I use kde 
That’s fine - I’m surprised you want a different dock, though. I don’t know KDE/Plasma so I can’t offer any alternatives. Try compiling - you might learn something
You could take a look at latte-dock, which is designed for the Plasma desktop. There is a bundle for it sudo swupd bundle-add latte-dock
You could take a look at the 0.9 release video to see if it’s something you’d be interested in.