You can change your profile picture by going to the 'My Page' and clicking the camera icon on the right. You can either select a picture from your photo album or take a picture and set it as your profile picture.
You can change your user name or status message by going to the 'My Page' and pressing the edit button. After you've changed your information, click the 'Complete' button at the button.
Please be advised that you can not edit your location or gender.