If you need to change your license key (i.e. you upgraded from a trial to a paid account), you can do that from the Setting screen:
Click the Gear
icon near the top-right corner of the dashboard.Select Setting.
Select the About tab.
Enter your license key in the LICENSE KEY field located under the About the deployment section.
Click the Change button. Once done, the dashboard will refresh and display the updated entitlements for your license key.