As you look at your tv there is a cabinet to the right. If you go along that cabinet all the way to the end and turn left, you can continue down that wall till you see the STOP sign , then hang a left to the locking release.
That's where the locking release 'might be'. If not, you will have to try to view some basic bracket styles used in rvs and try to find one that matches yours.
It has to have a locking release so you can lift up the tv to release it from the bracket to access your HDMI ports etc . See the link for vids.
http://www.tvformyrv.com/rv-tv-mounts-brackets/
