Changing your Captivate profile image is nice and easy once you're logged in.
To change your profile image:
Log in to your Captivate dashboard
Click My Account beneath your profile picture
Click the large profile image under Your Account
Find the replacement image you want to use
Click Open
An Upload Profile Picture window will appear
Adjust the image to suit
Click Save Picture
Scroll down to and click Update My Account
That's it - you're all set! 👍
Recommended Reading: Managing Your Captivate User Profile