How do I get my carrier code?

Excuse me, could you please clarify how one might obtain their carrier code? I'm a bit confused about the process and would appreciate any guidance you could provide. Is there a specific form I need to fill out, or is there a certain department I should contact? Additionally, are there any requirements or prerequisites that I need to meet in order to be eligible for a carrier code? I'm eager to get started and would appreciate any assistance you can offer. Thank you in advance for your help.