Hello. My name is Michael. I can help you with your question.
Normally what we would do with this is Export thenm from iPhoto into regular files like .PNG or JPG. Then to edit them in Photoshop, you would click on each one and then select the open in... and you can select photoshop. You could also associate certain file types with Photoshop but that might cause behavior you don't want, like opening every image you ever open right in Photoshop.