1. Login to your account
2. Click on options and select More options from drop down
3. Click view and edit your personal information
4. Select change right to password
5. Change password
6. On step 4 Check each change or Add links and verify that they are correct and change your security question and answer.
Or the simplest way, Go to https://account.live.com/ChangePassword.aspx, login and change password. (But i prefer you go the above method since it does not need to click on any external site, including mine)