You need to create a username and password when you first login to CCH Intelliconnect.
To get Tax cases from Nexis Uni, you should run the search on the topic you want after choosing Cases from the main menu. Then choose the Court (or courts) from the left hand panel (such as Board of Tax Appeals or Tax Court. You can also limit by publication date and the Practice area: Tax law.
If you need the FASB Codification use the database in the box above. If you are an Accounting student your instructor will provide you with login credentials.