If your account comes with the Miva E-Commerce software, just log into your WebControl System at http://your-domain.com/cgi-bin/plusmail and select script install than check Miva Merchant or Miva order and hit submit. The software will be installed within 15 minutes and you will find a directory called:
/Merchant2 for Miva Merchant
/Order for Miva Order
in your WWW when its completed. Your next step will be to register the product
For Miva Merchant - http://your-domain.com/Merchant2/setup.mv
For Miva Order - http://your-domain.com/Order/setup.mv