The Messaging section on the lefthand sidebar is where you will find create and send Push Notifications and access your messaging history.
The History tab lets you see your Scheduled Notifications, Geo-Fence Notifications and Past Notifications.
These are your Push Notifications that you have set up to send to a user's smartphone when they arrive or leave a location. You are able to Copy, Edit and Remove these from the History tab.
These are the Push Notifications that have already been delivered. You can see the date and time they were delivered. Click "Copy" to use this Push Notification again and simply follow the wizard!