The approval step Sends an email to the users in the selected group and waits for them to approve or reject the page. This step is blocking, in other words, the workflow will stop until the users in the selected group either accept or reject the page submitted to this workflow. When you add an approval step you will see a form similar to the following:
Simply click once on the users in the new window that must be notified to approve this page. Once they have all been selected, click on OK.