Here is how to upload photos on your wall.

Starting from your home screen, tap Progress from the bottom menu bar
Tap the + icon in the top right of your screen.
Next, tap the camera icon, just above the weight scroller
From here, you can choose to use a photo from you Camera Roll or take a new photo using your front or rear-facing camera.
Adjust your weight using the scroll wheel below
Finally, click the check (tick) mark at the top right to save your progress.