Login to your website

Click on the Admin Panel - > Permission button

At the bottom of the Revize Permission page, Click on the Add User or Role via AdminCenter

You will see the List of Users for your webspace

Click on the Edit button for the user you want to change the password for

Click on the Change Password option in the update user info page

Enter the new password and save

Now try login to your site with the userid and the new password.