Install elementary Tweaks for Elementary OS Loki

Elementary Tweaks is a tool that allows you to customize the elementary desktop as much you can possible and written in Vala, and released under the GPLv3. It used to customize common configuration options like, themes, icons, dock, window buttons, desktop effects etc.

$ sudo add-apt-repository ppa:philip.scott/elementary-tweaks
$ sudo apt-get update
$ sudo apt-get install elementary-tweaks