With the recent software update, some things have moved around a bit. If you are looking for how to update your profile, including the image that gets displayed for your avatar, just log in and then click on your name in the upper right hand corner of the site. From this screen you will see lots of new stuff.

 First of all, to edit your profile simply click the "Edit Profile" link towards the top of the page. You will be taken to a screen with several tabs, and the Manage Profile tab will be selected.  This contains all of the available profile fields.  Simply update the values as you like.  Your profile picture is at the end of the list - just click on the Upload File link, browse to the desired image from your local computer, and then click the Save File link to apply that image to your profile.  Once you have made all of your changes, click the Update button at the bottom of the screen to apply your changes.