How To Install Themes In Linux
To install themes in Linux, you can use Unity tweak tool or GNOME tweak tool. Unity and GNOME tweak tools are available in Software center.
Extract the theme file that you want to install like below -
After extracting theme file, open terminal and move extracted folder to /usr/share/themes.
$ sudo mv path-of-extracted-theme-folder /usr/share/themes
When you have moved folder, open Unity tweak tool or GNOME tweak tool that we installed above. Click 'Themes' in Unity tweak tool or 'Appearance' in GNOME Tweak tool and here you have the theme listed that you moved to themes directory.