On a Mac computer how do you add images to iPhoto?

If the image is already on the Mac you can drag it into the iPhoto icon in the Dock and it will be added to the iPhoto library. You can select Import To Library from iPhoto's File menu. Or select any Devices (cameras, phones etc.) that are connected to iPhoto and are shown in the left hand panel, then select the pictures you want to add and click the Import button.