This section of the "Sharing Options" page allows teachers to share generally with other teachers.
Here, set up a "Teacher Key" (a simple password) and share that with anyone you wish to allow to copy your plans into their account, or share/edit classes together with you using the "Replica" option. This key can be anything you want.
Using this method, all tabs/sections for your shared classes will be available for sharing.
To adjust the classes you wish to share, click on Go To -> Classes and click on a class there. Adjust the "Collaborate" section here to allow sharing.