I'm glad that link helped, now you've got a driver it should be possible to get it going under Linux. Unfortunately I don't know how to configure these modems, I would suggest running the setup program again and trying different options, if there are any questions you're not sure about try posting them here. Also, I saw there was quite a bit of documentation at that site, you might be able to find the answer there
As far as the /dev/modem link goes, its the same on my computer (ttyS1).
One other thing, if your modem has some lights on it you can check that they are lighting up when you plug it into the USB port, if they stay dead it may be something to do with hotplug/ hardware detection.