please can anyone told me where to put this code pls

loop-single
loop-single-premium
if like in item

You should have favorite item plugin, much better?

loop-single
loop-single-premium
if like in item

You should have favorite item plugin, much better?

Please in loop-single where should i place the code

You can place it i.e. after line:
<?php if(function_exists('fi_make_favorite')) { echo fi_make_favorite(); } ?>
And then format it by your needs.