Photo Stream

[adar]

Hi everyone, I recently upgraded to an iPhone 4S, and I am having difficulty with my photo stream. I have an iCloud account, and photo stream is on, although I do not back up to iCloud, I back up to iTunes. I have the most recent version of iPhoto, and I have both a camera roll album and photo stream album on my phone. But when I open iPhoto, I am not prompted to do anything re photo streaming. Any suggestions?
Thank you,
Ada