It’s now been close to a year since Microsoft introduced the app launcher in Office 365. SharePoint 2016 brings some of that goodness down to the on-premises world, but there are some caveats to watch for. By default, when installing SharePoint 2016, the app launcher is not available in the suite bar.
In order for it to appear, you need to go in Central Administration or to use PowerShell to provision an instance of the User Profile Service Application.
Doing this will automatically enable the app launcher in the suite bar.
Now, in the SharePoint 2016 IT Preview it is currently impossible for you to modify (add/remove) app tiles, but we can all assume that this will be made available to us once the final product ships.