I may be wrong, but I sort of remember that Linpus was based fedora at one point, so the instructions on this link may help:
http://www.techonia.com/install-huawei-usb-modem-fedora
It uses wvdial to do the actual connection work, and was an app I used for the usb-modem tethering back before Network Manager became so useful. If you do have a Network Manager that is in your menu with Linpus, you can try setting up the Mobile broadband section to see if it works. Since I don't have a Linpus install handy, step by step is difficult, but setting up mobile broadband usually only requires your username and password from your provider and hitting go. At least it was that simple with Verizon and my usb-modem connection. If you don't have a Network Manager, look at the instructions in the link I gave you and see if that helps.

Maybe someone who knows Linpus a bit more than I do can chime in and add some info.

I never used linpus linux. That being said, is Linpus available for downloading? Also, to clarify things, your modem is broadband based or dial-up?