Keep in mind that the end result is a digital audio file in some format. MP3 is the most common and easy to both create and put on your website. You can always convert the file format if you need to, so let's assume you will be creating an MP3.
Now that you know what you will end up with, what should you start off with? A script is a great idea, so you can practice and get it just right before you record. You can use an outline if you prefer. As long as you know what you want to say, and you can say it smoothly and convincingly.