How do I set up photo stream?

Question

In iphoto, when going into Preferences, there is only a tab for Mobile Me. I do not see a Photostream tab.
How do set up Photostream, now that mobile me no longer exists?
I have upgraded to Lion already, and I use icloud often for my mail, calendar, etc. but can't seem to get Photostream to show up in iPhoto or in icloud.

Answer 1

I quote:
Set up Photo Stream on a Mac to work with iPhoto
          Choose Apple menu > System Preferences, then click iCloud.
          Select the Photo Stream checkbox.
Open iPhoto (in your Applications folder).
               Select Photo Stream in the Source list on the left.
Click Turn On Photo Stream (on the right).  
By default, iPhoto automatically imports all Photo Stream photos into your library so you can keep them permanently, and automatically uploads every photo you import to your Photo Stream.
(The Forum software has munged the layout a bit, but you get the idea.) Please see the Apple Help page this comes from for more information:
http://help.apple.com/icloud/#mmbc40255b