Get SHIFT Panel Extension
To begin, visit https://exchange.adobe.com/creativecloud.details.104163.shift-panel.html which will send you to Shift Panel in the Adobe Exchange. This is available for Premiere Pro today, but will include other Adobe apps in the future.
Click the 'Free' option and once you have acquired the extension, you can view your Extensions by clicking the "View My Exchange" link.
In the next page, click the 'Sync' button and you will receive a green "Sync request has been sent" and you can find your extension in the Adobe app selected.
Install Shift Panel
Now that you have Shift Panel extension, you can go to Premiere Pro, navigate Window, Extensions, and click Shift in the dropdown menu. Keep in mind you can follow these steps with any of the Adobe Products: After Affects, Photoshop & Illustrator to generate the Shift token.
Once you click Shift in the menu, your Shift user profile via a token will be generated within the panel.
Because Shift supports a variety of different authentication methods, including social authentication and enterprise Single Sign-On, this simplifies the process of verifying your identity within the app.
To permit Shift access using this token, log into Shift in a web browser just like you normally would. Then in a second tab, open the URL given in the panel: https://app.shift.io/activate and enter your six digit token.
You will now be able to browse all projects and assets within the panel just as you would within Shift.