Please use this wonderful forum post to help you.

It took me just half an hour to get it working. not so in the past) much easier to set up PlexConnect in a Synology NAS ! So it is with much happiness when I found that it is (now. For me, the most important is still for the PlexConnect to pull the media from the PMS sitting in the Synology NAS, and not any Mac or PC. PlexConnect make use of some clever technical methods to overcome it. Plex is not an application offered by Apple TV3 so you cannot install it as a front end client to the PMS (Plex Media Server). PlexConnect is a workaround to use Plex on Apple TV3. I did this because I wanted to try PlexConnect. A waste as it is hard to find older Apple TV3 with older firmware now (usually Jailbreak works on older firmware). Took one of the Apple TV3 and updated the firmware (from 5.0 to 6.0.3).

A jailbreak to allow me to play XBMC on a 1080p Apple TV 3. I am still keeping them in the vain hope of a jailbreak on them soon. To install and configure your very own Plex Media Server on a Synology NAS, you'll need the following equipment.I have a few Apple TV3 at home. If you'd like to learn more about Plex, check out our guide on how to get started with Plex. Now you can enjoy access to all your content on your smart TV, Xbox One, tablet, smartphone, Windows 10 PC, laptop, and all other devices running the Plex app with adequate access. But you can create new folders in your 'home' folder that can then be accessed through Windows Explorer and other file managers for a more effortless transfer. The NAS itself comes with some default folders for such media, which can be selected. When running Plex on your Synology NAS, you will want to select a folder where Plex can keep track of media files, be it photos, music, or video. The truth is, Plex could be just what you're looking for to help you manage your media collection. Many of us might have passed it over for some reason, be it a lack of understanding of what it does, thinking it couldn't possibly be useful to you, or something else entirely. Plex is one of those services that has been around for some time. Source: Windows Central (Image credit: Source: Windows Central)

Plexconnect synology