Instructions
Go into your inventory by pressing "Start" or "1," then go to "Items." Select the smartphone, then unpause.
Scan around the area for the item you're supposed to be taking a picture of. The smartphone is only used under certain circumstances and a square will appear on the smartphone screen when you've found the right item to take a picture of. Stand at a medium distance or the phone will be too blurry or indistinct.
Press "A" to take a picture. Whenever this is necessary and has been done correctly, you'll be prompted that you completed the objective.