You need to pass Part 1 and 2 of the written exam and then get 2 years experience working for a registered agent. The most difficult is to pass the Test of Professional Competence (TPC). This is an oral exam where your "networking" is much more important than "competence" - who knows you vs what you know.

For REN you need to attend a two days training called Negotiator Certification Course and applied through a registered firm. Every E license holder could employ up to 30 REN and each registered firm location must have at least one E license holder.