To get started, go to Settings>Advanced>General>Optional Settings to enable the Pre-Approval process by checking the box, as shown below. (optional). When selected, the submitted event will show pending “pre-approval”. 

In addition, once an event has been approved by the Pre-approver and has gone through the normal workflow, sometimes changes can be made to the event by the owner of the event or Admin. If you'd like the changed event to go back through the pre-approval process, you should check the box shown below to activate this option. 

NOTE: The Pre-Approval process requires an additional level (first look) of approval prior to the typical approval workflow. This approval is done by a designated Admin(s) and/or Sub-Admin(s) that can assess the appropriateness of an event for their organization before it enters the normal approval workflow. Once activated, you will need to decide who will be the Pre-Approver(s) and give them user permissions in the User section of the Setup.

Next, an Admin must give user permissions to an Admin(s) and/or Sub-Admin(s) in Settings>Basic>Users to be a Pre-Approver (see below) and SAVE.