If you want to create a stream for PPC visitors, first you need to set up Google Keywords. (See here for how to set up Keywords for PPC/Adwords campaigns...)
Once you've set these up, to create the stream for your PPC/Adword visitors, you can go to Create Stream and (select from the list of filters) under "Referrers", "Custom: Google Keyword". Pick "with any selected value" and choose your keyword from the dropdown.
Simple! :)
I only see the following referrer options: Google campaign, Google Medium, Google Source, Google Term as options. Which one is now used for the keyword ?