Packages from the marketplace should always be placed in the /packages/ folder. That way all the custom blocks etc get installed with it (by installing it from the "Extend Concrete" page).

If you want to copy just the theme to your /application/themes/ folder for some reason, you can do that, but you'll need to edit the "page_theme.php" file in the theme folder.

Change the namespace to


The namespace is standard for all 5.7 themes that use the page_theme.php file.