As a foreign investor, can I file IRS tax returns online?

I am a foreigner who invested in some US stocks. I got some dividends last year and my broker withheld a certain amount for the IRS. They said I need to file a tax return with the IRS to get it back. What form do I fill? Or, even better, is there a software online that I can use? TurboTax does not seem to have options for non-US residents (or am I wrong)?