In the main GT Life screen, select Photo Travel and take a photo in whichever location takes your fancy, with your currently selected car, must be a "Premium". Make sure you have saved the photo.
Return back to the GT Life screen and select photo album, in the icons on the left. Press X on the photo to display full screen, press X again to bring up the options. Go to the left and click on Share.
Once it has uploaded you will get your trophy.
NOTE: You can also set the picture to be your profile picture here, if you so wish.