In your JW Player code, you'll have something like that

Hi tuji!
Here’s an example:

<div id='mediaspace'>bla bla bla...</div>

<script type='text/javascript'>
  jwplayer('mediaspace').setup({
    'flashplayer': 'https://xxxxxx/mediaplayer-viral/player.swf',
    'file': 'https://xxxxxx/video/xxxxxx.mp4',
    'image': 'https://xxxxxx/imgs/splash.jpg',
    'skin': 'https://xxxxxx/mediaplayer-viral/dangdang.swf',
    'controlbar': 'bottom',
    'width': '640',
    'height': '360',
    'stretching': 'exactfit',
    'plugins': {
    'related-1': {
           'file': 'https://YOUR-SITE/archives/category/THE-CATEGORY-SLUG/?feed=related-feed',
           'heading': 'bla bla bla...',
           'onclick': 'link',
           'dimensions': '210x161'
       }
     }
  });
</script>

Please, keep in mind that plugins in JWP code, like related, work only with the premium version of JW Player.
Hope this helps ??

Thank you very much but where this file exists? I mean in which file is this code?

You probably don’t know how JW Player works. You first have to download the player, upload the folder to your site and then use the above code in a file template of your theme.
Let me know news, ok?

I installed JW Player plugin using wordpress, then I changed ads edition and filled code. So now what can I change? thank you in advance and sorry for disturbing you.

If you use the official JW Player WordPress plugin, the only way to access to the code will be using plugin’s files.
This is not probably the best solution becouse you’ll lose your edit after update.
As I said before, you can download JWP from the official site, upload the folder, put a line of code in the header to call the script, and use the player code above.
See the JWP official documentation and remember, you need a premium version!

I have official JW player downloaded from wordpress and activated from official key, I just wonder where and in which file can I add the code, if in function.php of my theme where exactly or if in plugin’s any php file where exactly. can you help me? ??

Tuji, I think it’s better that you follow my suggestion, edit the official plugin it’s not a good idea.

I’m not going to edit something. I just have question: I installed JW player on my webpage: https://www.vinteo.ge

It works fine and its advert edition so it means it also premium edition.
My website uses wordpress engine, so I downloaded wordpres JW player and activated it.

After that I installed your plugin but dont have anything like related videos.
Plugin is fully installed and activated.

Why I cant see any related videos?
I need anything to change to show related videos? what can I change? which php or etc file exactly and where it exists?

Ok, don’t use the WordPress JW Player plugin, that’s where you have to start.
After that, follow the steps I told you, that’s it.
Hope you’ll find the solution ??