When you load the page www.netfirstplatinum.com there is a clear form for where each part of the form goes. Clear labels can be found for e-mail address, ZIP Code and pre-approval code. However, this is all that can be seen for someone without a credit card with them. I am assuming that you cannot get past this stage.
For the website's clear cut design it takes a while to find the help page for logging in (you may need to google search to find it yourself). There is a contact page (netfirstplatinum.com/contact.php) where you can contact the website directly. If this does not work you will be stuck because there is no other information regarding help logging in. If you can find no way of logging on, or finding other information using search engines a port of call might be:
Thehorizonoutlet.com as this is a partnet website with netfirstplatinum.com.