I should mention that yes, it is the same on Android.
To upload an image from your phone tap on the "hamburger", top left corner, to display the menu. You then select "Upload", then tap on "browse from your device". In Android you then tap on "File", I assume it is the same on iPhone, at that point you have to search for the photo you have taken. In Android it is also possible to take a photo directly into the "Upload".
Don't be afraid to play with it, you can always delete photos you don't really want on the system.