CRA MyBusiness Account

Sign up for a CRA My Business account - either register using the CRA Login or register using your online banking username/debit card information and password.

To register for the CRA Login, you will need your 

SIN
Postal Code
Date Of Birth
Tax information - amount entered on line 101 of your 2018 return - enter dollars only

Using the Sign-In partner is easier as you can sign in using online banking.

Sign up:
https://www.canada.ca/en/revenue-agency/services/e-services/e-services-businesses/business-account.html

Adding a Registered Business Number to your CRA account can be done using the steps outlined in the video below.