If you have Full Licenses, you can share access to them with other teachers in your organization. Navigate to the Student Licenses tab, then click the "Share Licenses" link below any group of licenses. This will popup a dialog that allows you to add teachers to the shared licenses.
You can only add teachers in your organization that have already created a Teacher Account (here's how). Once a teacher has been added to a shared license pool, they have the ability to use any of the licenses you've shared.
When a license has been used, it is not available to be used by another teacher until that teacher revokes the license from the student (see How to Transfer a License).