打开iTunes。 点击“商店”菜单。 填写表单。 填写付款信息。 验证帐户。

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
You can create an Apple ID directly from the iTunes application. Apple no longer uses iTunes-specific accounts, so you will be required to create an Apple ID, which works with all of your Apple devices. Select "Create Apple ID" from the menu. You will need to read and agree to the Terms and Conditions before you can proceed. After agreeing to the terms, you will be taken to a form that you will need to fill out with your account information. This includes a valid email address, a password, secur