Step 1:  Double click on the email with the picture you want to add to iPhoto. It should open in a separate window.

You should see the image in the body of the email.  (I just showed the top edge of one above.)

Step 2: Click on the image, hold it, and drag it down to the dock making sure the arrow pointer representing the mouse, goes right over top of the iPhoto icon in the dock.  Let go.   (This is called “dropping” the picture on the icon.)

iPhoto will open up and import the picture.   If you have more pictures to import, repeat the process, just drag and drop them onto the iPhoto icon on the dock.  In fact, you can even drag and drop a whole picture folder the same way.

OS X often provides more than one way of doing something.  The same goes for importing photos into the iPhoto program.   Here is the easiest way.