Not everyone is required to fill out of W8-BEN, it depends on your tax situation, so you have to setup your tax information in the contracts module of itunes connect once you have accepted your contract, you can go through the series of questions and based on the answers, you would be taken to the relevant tax form.
How to sign up for a paid books account if you are not a US citizen:
See this FAQ.
You will need an EIN from the IRS/US Govt., which you can obtain over the phone. If you attempt to publish as a company with Apple, you will be expected to show proof. Scan the relevant documents and send to Apple per their instructions.
Know that at this time, there are 32 stores are available for publishing/distribution, basically US, Canada, Australia, and most of Europe.