You can activate a page two ways. The first method is to activate from the Websites pane in CQ. When you click on a page, there is an Activate button on the toolbar across the top. You can also right-click a page and choose Activate.
Activation can also be done without leaving Author mode. Simply click on the Page tab of the Sidekick (second icon from the left), and click Activate Page. When performing an activation, a small message should appear in the top left to confirm the activation was successful.