subtitle position and size

[xpender]

Hello,
I have an UE40D5000 connected to my router via lan.
I am able to play mkv with subtitles from my NAS, but the subtitle is a litle bit small and positioned near center.
I will do the trick, but I need your help to forward me to a link with installation guide and patch.
I guess, as long as Samsung set the size and position of subtitle, it can be changed.
Please help.
Kind regards.