If you are using sublime package control, you can install directly from the Package Control: Install Package
menu item.
The theme is listed as Theme - Numix
in the packages list.
To enable the theme and adjust theme settings edit your Preferences.sublime-settings
file:
"theme": "Numix.sublime-theme"
// small tabs
"numix_small_tabs": true
"numix_xsmall_tabs": true
// Sidebar padding options
"numix_sidebar_tree_xsmall": true
"numix_sidebar_tree_small": true
"numix_sidebar_tree_medium": true
"numix_sidebar_tree_large": true
"numix_sidebar_tree_xlarge": true