On the left hand side of the editor you will be able to view already uploaded images, as well as add new images. Just click on the blue photo icon and you will see an option come up asking where you would like to select your images from!
Upload: Choose from a location on your computer or hard drive.
Existing Projects: Select images from your existing projects. When you select this option a window will pop up showing you your previous orders and images and you can select the images from there.
Facebook: Upload images form your photo albums on your Facebook. You will need to sign into your Facebook account in order for the editor to have access to this.
Once you have uploaded the images you wish to start with you can begin building your album!