Newie Customisations not being picked up.

I've got a fresh install of 1.3.8 and I'm new to working with Zen Cart, install went great, I've just been going a little crazy trying to make my first customisations.

I haven't done anything with it as yet. I'm right at the beginning and am trying to change the "Congratulations! You have succ...." message.

I've customised index.php as per the tutorial at https://www.zen-cart.com/tutorials/index.php?article=129

i've updated /var/www/html/includes/languages/english/index.php
with my own greeting instead of "Congratulations! You have succ..."
i've saved the customised version in /var/www/html/includes/languages/english/custom/index.php

It doesn't seem to pick up the CUSTOM versions. Any thoughts as to why? I'd be very grateful if you have any ideas.

If I modify /var/www/html/includes/languages/english/index.php the changes do get picked up, if I delete it the tags are undefined but it never picks up the CUSTOM version. Is there a definition I need to set to get it to pick it up?

Thanks if you have any ideas that will help solve my problem. I don't want to go editing the base files directly and invalidating my upgrade capability. Any help much appreciated

If you haven't set up your template in includes/templates named CUSTOM, with the identifying template_info.php file, and designated it as your template in Admin/Tools/Template Selection, then Zen Cart doesn't know to look for folders named CUSTOM.

Search the Tutorials/FAQs for "override system" for articles on how to set up your custom template override folders.