How do I download my photos from iCloud to my iPhone?

I just got a new iPhone 6s and I restored all my data from my old iPhone 6 and iCloud account, but I want to actually download the photos I have stored in my iCloud account to my iPhone. I had a 16GB iPhone 6 and had have about 10GB of content in iCloud. I want to actually download those photos to my new 64GB iPhone 6s because I now have the room but all of my iCloud photos that show on my phone have a small exclamation point symbol in the bottom right corner and I can't seem to find out how to get them downloaded. Can anyone help?