A full video guide is available on this link: http://www.youtube.com/watch?v=4Y6EcOM_F10
1. Log in into your Paypal account at www.Paypal.com and click on the "Merchant Services" tab.
2. If you already have a "Buy Now" button which you've created, click on it. Otherwise, create a new "Buy now" button by clicking the "Buy Now Buttons" link.
3. If you're creating a new "Buy Now" button, choose a name for it. Fill in the relevant fields and click on "Create Button".
4. Select the HTML code you now see on your screen and copy it.