Let`s take a step back here.
You are asking how to make your laptop wireless.
If all you have is a usb modem connected to broadband internet simply you cannot.
You would connect the broadband from a telephone line or fiber optic cable then connect the modem to your laptop via the Usb connector from the modem.
The only way to get wireless if you wanted it would be to buy a router that has Usb ports on it and then connect the modem to the router and then setup a wireless through the router for wi-fi to the laptop. Or buy a new combined modem/router box with wi-fi.