Step 1: Click the plus sign in the middle of the photo slot.
Step 2: You will be taken to your Gallery, but you can choose to upload photos from your desktop. You can also choose to select your photos from either your Gallery, Albums, People or Tags.
Step 3: Once you locate the photo you want to add, simply click on it, and it will be added to your project.
Step 4: Move to the next photo slot you want to fille and repeat from Step 1!