To change a user's sharepoint password, follow these steps:
1. Log in to the sharepoint site as the user you are changing the password for.
2. Click on the Site Settings link.
3. Under Manage My Information, click Update my information.
4. Click on the Change Password link.
5. Fill in the fields with your old and new passwords.
6. Click OK Alternatively,

if the password has been forgotten, the Administrator for the site must follow these steps:
1. Log in to the site using the Admin login (site collection administrator).
2. From the main menu, click on "Site Settings".
3. Under the "Manage My Information" sub-heading, click on "View Information About Site Users".
4. Click on the User ID that requires the password change.
5. Click on "Change Password"
6. Enter the new password as per prompt.
7. Inform user of new password.