I am unfamiluar with this particular modem but does it authenticate from your computer or is the user name and password written to the modems software? If it is done through the modem software then you should only have to connect one comuter to the modem via USb and the other via an ethernet cable to the modems ethernet port as per specifications and they should both then be connected directly to the internet. a friend does it that way using a Netcomm 1300.
Allen