Adding translations for posts and events work in the same manner.
First you need to publish an event/post. Only after an event/post is published you can add the translation. To learn how to create an event (and all the details you need to fill in) see this page, on how to create a post see this page.
Once you have published the event, edit it to add a translation.
During editing of the event you can see in the sidebar the language box:
To add a Dutch translation to this English page you click the “+” after “Dutch”:
You then need to fill in the title, and text. Other stuff such as the featured image should be set if you had set it in the original article. Do not forget to publish the article after you have entered the translated texts.
Note that if an event/post already has a translation the language box looks slightly different. For example below you see a Dutch article, for which an English article already exists. You can press the 🔄 after “English” to go and edit/update the English translation.
We use the WMPL plugin, so you can check the official documentation as well. You can also ask on the #tech-public channel.