Create a new profile
In order to create a new profile, you use the Profile Manager. To start the Profile Manager in Windows,
follow these steps:
Close Firefox completely (select File > Exit
from the main menu of Firefox).
Select Start > Run... from the Windows Start menu (use the search box on Vista).
Enter firefox.exe -ProfileManager and press OK.
On Linux or Mac, start Firefox with the
-ProfileManager switch, e.g. ./firefox -ProfileManager (this assumes that you're in the firefox directory).
You should now see the Profile Manager window, shown in the screenshot to the right.
From the Profile Manager you are also able to remove and rename profiles. Be very careful when deleting profiles; if you created the profile in an directory that already existed, the entire directory will be removed!