I tried sharing a course I created outside of Thinkzoom, but I do not see the link tab under the share button.

To share a course outside of Thinkzoom that you created with our course builder, make sure that you have enabled all associated content with that course to be shared this includes any videos, documents, PDFs.  

To enable sharing, you will need to go to the file in the Add Content section, select the file and check the Allow Sharing button.

When all the content in the course has "sharing enabled," a link will be available in the Share button to send out.