The first way is the following:
1. Click on the "Account" Tab on the top right
2. Now click on "My Profile" icon
3. You will see a "General" tab where you will have two sections
"General Information" - Here you can change your e-mail address
"Panel Preferences" - Here you can change your password for logging into the panel (not your hosting subscriptions) and your Panel Language.
The second way to change your Contact and Password information in Plesk 10 is to do the following.
1. Find your user name on the top right of the screen
2. Click on your user name and it will take you to the same area as the first way described above.
2. Click on your user name and it will take you to the same area as the first way described above.