To update your avatar, first click on your name located in the top right corner of the screen, then proceed to the "Profile" section. In the profile page's top left-hand corner, you will see your current avatar (or a default image if you haven't set one up yet). Below the avatar, a small gray "Edit" button allows you to change this image. Click on it to choose and upload a new photo directly from your device, or to import one using a URL.