How do I buy Crypto on BitPay?

As a newcomer to the world of cryptocurrency, I'm wondering how I can purchase digital currencies on BitPay. Could you please explain the step-by-step process in a concise manner? I'd like to know what kind of accounts or registrations are required, if there are any transaction fees, and how secure the platform is for making such purchases. Additionally, are there any specific cryptocurrencies that BitPay supports, and are there any limitations or restrictions I should be aware of? Understanding these aspects will help me make an informed decision and ensure a smooth buying experience on BitPay.