Step1: File menu
Selecting the File menu from the menubar and clicking Import will bring up the standard OS X Open window to enable you to add multiple photos quickly and easily.
Step 2: Select and Import
All you need to do is find the file containing your photos, then head up to Edit and choose Select All. This will highlight all the images, so all that’s left to be done is to click Import.
Step 3: Drag and drop
For a much easier way to add your Photos, locate them in the Finder and simply drag and drop them into the Events section of the iPhoto window. They will be instantly added to your Library.