What jschiwal is saying is....you need to be in that directory with the "inf" file in order to run that command. So lets say you have a folder on your desktop called "broadcom_driver" with the inf file in it. cd to that directory and try running your ndiswrapper command again. Also, just out of curiosity, what kinda of Broadcom is it? What does
sudo lspci | grep -i network
show? The reason I ask is, I just posted a thread about the 4310 that is a nightmare to get going unless you have the exact driver.