I'm assuming you are installing to a live server rather than a test on your own system.
In order it's quite simple.
1. Ftp the complete ps3 download to your HTdocs directory on your web server (this may take some time)
2. COntact your ISP and request a mysql database they will supply you with the following:
Database location ie an ip address
3. Open up your web browser and type in your domainname.com
4. By default the webserver will be set to open a default file of index.php
5. Index.php will open and run a quick test it will ascertain that you have no database connection setup. It will run through the setup and configure your site. (it will ask you for the details from 2)
6. When setup is finished you will be in the admin section where you can add products and alter the content using theCMS.
OK thats it a simple shop setup. From here on it you can change oodles of things:
Use the CMS to change content
Use the CSS to change colours layout
As a personal preference I set shipping and payment to none during the setup and then when I* have the design stc correct implement paypal etc.
If you need any mopre help just post