Customizing a theme

Hi, I would like to make small changes to the antimatter theme.

As per:
https://learn.getgrav.org/themes/theme-configuration

To not lose changes if the theme is updated, I tried placing eg:

blog_item.html.twig

in:

/user/config/themes/antimatter

The theme does not seem to pick up changes made to this file.

Then I tried placing it in

/user/config/themes/

But the theme does not seem to pick up changes made to this file either.

Please help.

Create a new theme based on antimatter and change all you need to.
https://learn.getgrav.org/themes/customization

Ah, thanks so much for pointing that out....

I should rtfm more :)