if you need to create completely new account:

Log out and Create New Account

You must logout from your iPhone/iPod touch in order to unsubscribe from Apple's Push Notification Service (APNS). To logout:

1. Login to myPhoneDesktop iPhone/iPod touch app
2. Tap Settings
3. Tap your account name (user Name, under Settings | Account Section)
4. Tap Logout

After you logout you can tap Create Account to create New Account (see "Create/Edit Account" topic here: http://support.myphonedesktop.com/entries/109057-how-to-create-or-e...)