To un-share a review, there are 2 options:
1. You can un-share the same way you had shared in the first place. Press the Results button for the given employee on the Appraisals page.
Once on the Results page, click the Share button again at the top of the screen. Note that approvals may have to be revoked first before unsharing is allowed (see option 2 below if this applies to you).
Then, switch the state back to "Not shared" and press Save.
2. Use the Workflow button to un-share the review after pressing the Edit button for a given reviewee on the Appraisals page. Note that signatures must first be revoked before unsharing is allowed.