How to connect iMac using virgin mobile broadband 2 go

I'm not the sharpest tool in the shed when it comes to computers. That is complicate things I am changing from a PC to iMac MC309LL/A 21.5 Desktop.

I use Virgin Mobile Broadband 2 Go, USB device to connect to the net. I've been able to install and set up the Broadband 2 Go on the Mac. The Connection

Manager comes up on the screen, however when clicking "Connec", nothing happens. I know the device works cause I'm using it now on my PC. What am

I not doing, or what am I doing wrongn ?