[Plugin: Custom Field Template] How to display custom fields? I get Fatal error

first of all Hello there..this is my first post

I was trying to display custom field values on my post, I was working by this tutorial https://www.youtube.com/watch?v=L3VXnryN9iY and i’ve put code in functions.php and singleSmjestaj.php which is a copy of template.php just for that single category (this template is pretty weird so everything that should be in single.php is in template.php and stuff like that)

you can see the code on 2:20 and 3:40 of the tutorial

I keep getting the error “Fatal error: Call to undefined function getCustomField() in /home/sabmedia/public_html/sabunike/wp-content/themes/easel/singleSmjestaj.php on line 44”

My theme: Easel
https://www.ads-software.com/extend/themes/easel

I’m not even sure if the functions.php is the file where I should put the first part of the code or not

Please help me I can’t figure this out
P.S. sorry on my bad english

https://www.ads-software.com/extend/plugins/custom-field-template/

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