To set the language, just choose it the dropdown list in the Languages box on the top right of the ‘edit post’ panel.
For each language you have three options:
- Do nothing if you don’t want to translate your post.
- Choose, thanks to the autocomplete input field, an already existing post as translation.
- If you want to create a new translation, just click on the + link in the right language. If translated categories and post tags are available, they will be automatically set in the post translation. The same for page parent.
The operation for pages and custom post types is exactly the same.
Note that the categories are filtered according to the post’s language. The same for the tag cloud. If you create new categories or post tags, they will be automatically in the current post’s language. However, you will have to go on the Categories (or Post tags) admin panel to set translations if needed.