See
Bug 35700 - Admin Console work for Share management and discovery. and the release notes for your version of GnR.
The instructions aren't very detailed, but this is how it works:
1. In Admin GUI, go to Distribution Lists, select the distribution list, and click Edit.
2. Click the Shares tab.
3. Click Publish New Share.
4. Enter the email address of the owner of the share you want to publish. Then click "Find Shares.
5. Select the shares you want to publish and click "Publish Selected Shares", or simply click "Publish All Shares".
Note that this interface also lets you tell ZCS to send emails to new members of a DL regarding published shares.