Current Post URL at the end of Every post ?

In the template file, you can add in something like this:

<p><?php echo the_permalink(); ?></p>

In Index.php file or in different file ? can you tell me the filename

I can’t tell you the file name. That dpeends on your theme and how it’s set out. It could be any one or more of a wide range of files.

if I had to guess, I’d be looking for either content.php or content-post.php or some combination like that. Like I sid, it all depends on how your theme is set up.