1. Download and extract the installer
2. Run the SetupRevengeOfTheTitansHIB-18012.exe and install.
3. Enjoy the game!

"At first they came from the skies. In the ensuing war, Earth was laid waste, but we had won...

But that was just the first strike - now the invasion has landed! Defeat the returning Titan horde in a series of epic ground battles, save the Earth, again, and command the counterstrike against their homeworld!"
 
http://www.puppygames.net/revenge-of-the-titans/

"Construct and command your ground defences in a series of increasingly massive battles across the solar system, in our frenetic arcade mash-up of Real Time Strategy and Tower Defence!"