The documentation on this is here: https://wp-events-plugin.com/documentation/using-template-files/
You can place the template overrides in one of the following locations:
- wp-content/plugin-templates/events-manager
- wp-content/themes/parent-theme/plugins/events-manager
- wp-content/themes/child-theme/plugins/events-manager
In your example event_list_item_format.php would be copied to any one of the following directories:
- wp-content/plugin-templates/events-manager/formats
- wp-content/themes/parent-theme/plugins/events-manager/formats
- wp-content/themes/child-theme/plugins/events-manager/formats
Read the wp-content\plugins\events-manager\templates\formats\readme.txt file to see how to override the files in this directory. For the override of event_list_item_format.php you would need to add the following code snippet:
function my_em_custom_formats( $array ){
$my_formats = array('dbem_event_list_item_format'); //the format you want to override, corresponding to file above.
return $array + $my_formats; //return the default array and your formats.
}
add_filter('em_formats_filter', 'my_em_custom_formats', 1, 1);
You can use the Code Snippets plugin to add the above code snippet.