To access data from a previous year, use the "Year" drop down menu from the Home page. Either the Home page will load automatically after you long in, or you can access it by clicking the "Home" link on the main navigation pane.
On the top left side of the home page, select the Year drop down menu and select a previous year.
Then, select the year you wish to view the previous year data of. Once you select that year, you'll be redirected to the interface for that year, with all its original documents retained. You can verify that you've been moved to your year of choice by checking the year beside the entity name you're assigned to.