The first thing you will need to join BizSpark is a Microsoft Account. What is a Microsoft Account? It's what you use to sign in to Microsoft devices & services like Outlook, Skype, OneDrive, Office 365 and of course BizSpark.
You may already have a personal account (such as you@outlook.com); however it's recommended that you create one for your startup so that you don't run into issues like having to share your password or linking your company to your personal email/One Drive etc.