Please post the results of "lsusb". The first step is to identify the hardware. Sometimes the kernel has a module for a device, but you need to install firmware before the device can be used. Also run yast2 network and see if the device is listed.
Run "dmesg | grep usb | grep modem". You may see something about a connected usb tty device.
The modem may be detected and you need to configure it in network manager. Here is a list of devices known to work: