There's 2 ways to upload pictures on this site. Go to your own page by clicking on your name. Then on the left menu, click on pinboards. You'll note the button upload pictures, click that and follow the directions.

The second way is to attach a picture when you post a status on the activity. But you can only post a picture one at a time this way. However then it will show up on the activity feed so more people will see it.