How do I apply for a referral?

Excuse me, could you please explain the process of applying for a referral in more detail? I'm a bit confused about the steps I need to take. Do I need to fill out a specific form? Do I need to provide any additional documents? Is there a specific timeframe in which I need to submit my application? I'd appreciate it if you could walk me through the entire process, from start to finish. Thank you in advance for your help.