How to link test set (and test cases) to a release?

I have a release set up but no test cases appear in the Release  'Test Cases' tab.

I have an existing Test Set (it is a clone of a similar one) that references the Release number in the Overview tab, properties section.

How can I get the test cases to show up in the release - test cases?

Do I have to manually add the test cases to the release through the test cases page?  There is the Test Cases->Tools->Add To Release feature there.  There are several hundred test cases to add.