How to use Coinbase promo code?

Could you please guide me on how to effectively utilize a Coinbase promo code? I've heard it can offer some great discounts and bonuses, but I'm not quite sure where to start. Do I need to enter the code during the sign-up process? Or can I apply it later on after creating my account? Also, are there any specific conditions or terms I should be aware of before applying the code? I want to make sure I don't miss out on any benefits and that I use the code correctly. Could you provide a step-by-step process on how to do this? Thank you in advance for your assistance!