In a Teamwork project, there are two Publisher Set modes: Public Sets and My Sets. Shared Publisher Sets must be placed in the Public Sets list.
Since there can be multiple public Publisher sets, you must specify which one you want to reserve. Navigate to Public Sets Management (use the “One Level Up” button) to see the list of public Publisher Sets.
From the Public Sets Management list, choose the desired Publisher Set. Click Reserve at the bottom of the Publisher Set page to reserve it; or click Reserve from the context menu.