Multilingual pages
To add a new language, click on the language next to the Pages then select add a new language.
When you add a new language to your website, keep in mind that all of the website's current content and pages are copied over into the new language you've created.
This also means that you should make sure the content is finished in your default language first to avoid redoing content.
Multilingual URLs
Let's say you want to add German to your English website.
Your (English) website:
www.domain.ltdwww.domain.ltd/contactwww.domain.ltd/privacy
When you add German and you swap to the de locale in the quick swapper:
www.domain.ltd/dewww.domain.ltd/de/contactwww.domain.ltd/de/privacy
The pages will automatically be linked as alternates. www.domain.ltd/de/contact will be an alternate of www.domain.ltd/contact, and so on.