If you want to add some new custom changes, you need to add a new custom php file for that page in themes/functions/ folder with name custom_tpl_articles.php, where you can add the new changes and define those to a template variable. Also you should place that variable in themes/{Current theme}/articles/ topics_article_info.tpl

1) {$topic_heading_title} - To display the title of topic as page heading. If topic heading is not present, then HEADING_TITLE will show as page heading.

2) {$authors_name_text} – To display the author’s name if the topic have.

3) {$articles_filter} – To display the dropdown menu for filtering by authors/topics. This will show only when Display Topic/Author Filter is set to true from admin -> c settings -> settings ->shop systems -> Article configuration tab.

4) {$topics_description_text} – To display the description about topics.

5) {$authors_description_text} – To display the description about authors, if present.

6) {$authors_url_text} – To display the author’s url, if present.