Here is how to upgrade from the Legacy Starter plan:
1. Go to the Burger menu 
at the top right of the screen and then click on Account administration.
2. Click on User management 
3. Click on the name of the user whose subscription plan you wish to upgrade.
4. Click on the Subscription level field, change it from Starter to Pro and click Save.
Make sure that you do this for all users on the same level (Company or Location).