The Fact Sheet (FS-2016-20) issued with the News Release contains the following details on accessing and using the system.

Here’s what new users need to get started:

A readily available email address;
Your Social Security number or Individual Tax Identification Number;
Your filing status and address from your last-filed tax return;
Access to certain account numbers for either a credit card, home mortgage loan, home equity (second mortgage) loan, home equity line of credit (HELOC), or car loan
A readily available mobile phone. Only U.S-based mobile phones may be used. Your name must be associated with the mobile phone account. Landlines, Skype, Google Voice or similar virtual phones as well as phones associated with pay-as-you-go plans cannot be used;
If you have a “credit freeze” on your credit records through Equifax, it must be temporarily lifted before you can successfully complete this process.

Because this process involves verification using financial records, there may be a “soft notice” placed on your credit report. This notice does not affect your credit score.

To securely access Get Transcript Online, first-time users must:

Submit their name and email address to receive a confirmation code;
Enter the emailed confirmation code;
Provide their SSN, date of birth, filing status and address on the last filed tax return;
Provide some financial account information for verification such as the last eight digits of their credit card number or car loan number or home mortgage account number or home equity (second mortgage) loan number;
Enter a mobile phone number to receive a six-digit activation code via text message;
Enter the activation code;
Create username and password, create a site phrase and select a site image.

Returning taxpayers who have not completed the new secure access process:

Log in with an existing username and password;
Submit financial account information for verification, for example, the last eight digits of a credit card number or car loan number or home mortgage account number or home equity (second mortgage) loan account number;
Submit a mobile phone number to receive an activation code via text;
Enter the activation code.

Returning taxpayers who have completed the new secure access process:

Log in with an existing username and password;
Receive a security code text via mobile phone provided with account set up;
Enter the security code into secure access.