Thetis is an icon pack. It is not a stand alone application you need a third party launcher to apply it.

What's included:

★ 3.500 + HD icons (256x256)
★ Matching HD cloud wallpapers!
★ Launchers support: Action Adw AdwEX Apex Atom Aviate GO NextNova Smart Solo...
★ Icon masking for un-themed icons
★ Dynamic calendar (For Nova Launcher)
★ Alternative icons to choose
★ Updates.