If you are an active SPC, you can exchange licenses through the Course Admin page:
Log in to Studio
Click on Teach & Manage > Course Admin tab
Navigate to the License Management section
Click the Exchange Licenses button
IMPORTANT: Courseware is not awarded for an exchanged license. You still must purchase at least one license to be awarded the courseware.
NOTE: In general, 2-day course licenses can only be exchanged for other 2-day course licenses, 3-day course licenses can only be exchanged for other 3-day course licenses, etc.