Click on Trackers, then click on the trackers you want to add collaborators to.
Hover over the menu button and click on Add Collaborators.
Enter the names of teachers, schools, or districts to search for the educators you want to add as collaborators. Once you've selected who you want to add, click on Update. Those teachers can now add to and edit your tracker.
To see any trackers you are collaborating on, click on Trackers to see your full list of trackers, then click on Collaborating On.