you want to print the pictures you have in iPhoto, select the images
that you want to print. Next go to the File menu and choose "Order
Prints." iPhoto will then connect you to Apple's photo printing service.
You will need to create an account to order prints. Once you set up
the account you can choose what size and quantity you want to print
your order. This is the easiest way to order prints of your pictures.
However, if you wish to use a 3rd party printing service, such as kodakgallery.com
or costco.com, etc. you will need to export your photos and then upload
them. Select the files you want to print and then either export them
or just drag them to the desktop. Now when you go to the website of
the printing service of your choice, you will upload these photos from
the desktop. You will need an account at any of these websites, once
it's set up, upload your photos from the desktop and place your order.
After your files have been uploaded you can delete the duplicate photos
on your desktop. The originals will still be in your iPhoto library.