If you're using an older computer & operating system, you might be able to download a free-trial of CS6 instead. Just be sure to follow the VERY IMPORTANT INSTRUCTIONS.
CS6 Direct Downloads
http://prodesigntools.com/adobe-cs6-direct-download-links.html
CS6 Suite's Tech Specs
http://prodesigntools.com/products/adobe-cs6-system-requirements.html
Once your product(s) are installed on your computer, you launch them the same way you launch any software, via the desktop shortcut or from Program Files (win) or Applications folder (mac).
Nancy O.