Please visit the DIRECTV NOW support experience on att.com.
You can order DIRECTV NOW whether or not you're an AT&T or DIRECTV customer. DIRECTV NOW is a separate service that is billed separately from any other account. You can even add your DIRECTV NOW account to your existing AT&T Access ID when signing up. This way, you can manage all accounts with a single ID.
For pricing options, plan comparisons and to sign up, please visit DIRECTV NOW. Once your account is created, you can stream immediately.