WPX Hosting Affiliate program is open for both customers and non-customers. You can create an account here, or request access through a support ticket.
All of the information needed can be found either in our Affiliate knowledgebase section or our Affiliate hub which looks as shown below.

If you have any other questions on the topic, get in touch with WPX Support Team via live chat or a support ticket. For direct email correspondence, please use the following address: ivanina.heppt@wpx.net.