In the menu Builder > Sections, select your mCMS Article section in the list of sections.
Click it to display the sub-menus "List of Articles" and "Article", and click "Article".
It is only possible to modify the date or author display with templates 1, 2, or 3 (you can check which template you use in the tab Template of your section).
Then click your template. At the bottom of the page click HTML Code menu.
1. Delete the date
To delete the date, delete exactly the portion of the code <div class="date">Rédigé le [DATE]</div> in the HTML Code menu, then click OK.
2. Delete the author
To delete the author, delete exactly the portion of code <div class="author">[AUTHOR]</div> in the HTML Code menu, then click OK.