Download the Hybrid RocketLauncher Package (rt_hybrid_wp_rocketlauncher.zip) from the Hybrid theme downloads section
Unzip the zip packaged onto your computer to reveal the rt_hybrid_wp_rocketlauncher folder
Upload this to your site using your FTP client
Direct your browser to the installation such as
www.yoursite.com/rt_hybrid_wp_rocketlauncher
or to whatever directory your uploaded to
Follow the standard WordPress installation, after which the theme and gantry framework will automatically be activated, along with the sample content.
I did one install the other day with no problem. If you get stuck let me know and I will see if I can help further.