I would like an appraisal. How do I begin

You could also call them and ask what the procedure is for your specific item. Cuts down on unnecessary time. If it's not in their purvey, then ask them for a referral. Good luck!

I have a rare coin and need to get it appraised Can you help me?

Go to their website, depending on what you would like to consign, you may be able to submit a picture and description and request a pre-sale estimate.