I haven't actually added any photos yet, but another user recently answered this same question:
Click on the person you want to update. On the left side of the screen an option box will appear. The first button says "Add photo for [name of person]". The photo you add has to be on your computer. Click on the "Choose file" button. This will open a dialog box to find your photo. Navigate to your chosen photo is located, click on the photo and click "Open". this will bring you back to the second box where you will click on the "Upload" button.