Within Teamwork Desk, you can switch between the classic version and Teamwork Desk 2.0 via your profile.
Click your profile icon in the top right of your site.
At the bottom of the dropdown menu, the switch option will update depending on the version you are currently in.
Once you select to switch, the site will reload, bringing you to the alternative version.
When using Desk Classic, you will also have the option to switch to Desk 2.0 from the navigation bar.
For more information, see: Teamwork Desk 2.0 Overview