Flock works on the same basis as Google Chrome (the interface is similar) except that it has been optimize for easy access to social network and instant messaging tools...
To set your homepage e.g http://www.google.com/ underFlock simply:
Click on the "Customize and control Flock" button
In the dialog that opens select the "Basics" tab.
Down in the "Homepage" section check the "Open this page" option and paste the URL of your homepage in the appropriate field:
Validate with the OK button.
Using Multiple Homepage
In the "Basics" tab
In the "On startup" section, check the "Open the following pages " options.
Click on the "Add" button and enter the URL of your favorite websites: