Customise Wingpanel step-by-step

A lot of people ask how to change the colour and style of wingpanel in elementaryOS so here is a little tutorial to explain how it's done.

YOU WILL NEED:
A file manager (this tutorial uses elementary's pantheon-files)
A terminal
A text editor
Elementary Tweaks:
    sudo apt-add-repository ppa:versable/elementary-update
    sudo apt-get update
    sudo apt-get install elementary-tweaks

I've included a .zip that contains the Milk Light theme I made in this (just copy it in (as an admin) with the rest of the themes in /usr/share/themes),
this tutorial and a separate copy of the "apps.css" file you use to customise the panel in case you want to play around without changing anything.

Wall: Derevo by ASIAONLY