To add an article in the section Projects, Demonstrations, Evaluations, Events, Publications… Create a “new article”, then in the margin to the right of the editor, “document” tab, associate it with the corresponding category.

Since the site is bilingual, each page and article requires a French version and an English version (after publishing your article in the first language, you can, in the list of articles, copy and paste it, then edit the copy and check the second language in the right margin (“document” tab) before doing the translation.

Help to use WordPress editor (Gutenberg):
https://fr.support.wordpress.com/editeur-wordpress/