How do I add keywords to iPhoto images using Automator
If you are using the “Import to iPhoto” Automator action, that returns a list of iPhoto photos you can process. Just add an “Applescript” action after your import action with the following script:

tell application "iPhoto"
    repeat with importedPhoto in (input as list)
        select importedPhoto
        assign keyword string "your keyword"
    end repeat
end tell


– that should do the trick.