Set manual local IP-adress to Plex (and to get it to work with remote access using OPEN VPN)

Hi!

I have Synology DS1515+. DSM 5.2-5644 Update 5
I connected two ethernet cables so I have two ip-adresses. Plex is using one of them.

1. Is there a way to me to manually change the ip-adress plex shoud be using locally on this NAS?
2. Does someone have any experience using an Open VPN service and to get remote access to work. Any ideas, anyone? Is it even possible?

My idea was that maybe I could get the second local ip-adress on the NAS to not use the VPN in someway.
But I don't even know if thats possible in the first place.

Very thankful for answers.