I just bought a late 2011 Mac(for $5) which was running El Capitan, but is now running High Sierra, anyway, being new to Mac OS, I am a bit stumped on how to get the dock unlocked, as when I got the Mac it wasn't even cleared of the past user and even though I found a command to get the Mac to create a new user from entering commands in Terminal some of the last users software is still present and still on the dock, which I would like to remove and customise it to the way I want it. I have tried Onyx and Terminal commands found online, but they haven't worked. Help!

