Tascam US-122 and no sound.

I´ve got an external soundcard called Tascam US-122 and the software Cubasis VST bundled-version. US-122 is connected to the computer through USB-port. The thing is that I can´t get it work. It´s nothing wrong with my guitar. The signal is coming into the computer, coz I can use the tuner in the program. Is there any settings that I have to change? Please help me or I throw my computer, guitar and US-122 out the window.
I´m a novice on computers and musicsoftwares so please use a language that is not to complex. Or write in swedish
/Martin