You can sign up for a Sandbox Account here
After you sign up successfully, you should receive an email with instructions to create Sandbox Account on Enterprise Business Portal
If you do not receive an email,
Smartpay Fuse's Response code page provides
Smartpay Fuse's Flex Microform solution provides tools to build PCI-compliant sites and apps. To understand all of the options available to you, see our Flex microform documentation.
You are responsible for maintaining communication with Smartpay Fuse servers. Set your client applications that communicate with Smartpay Fuse to direct requests to a host name and not an IP address.