There are two ways to make a multilingual website on Tilda. You can either make several copies of your websites in different languages with separate domains, or create several pages within a single website.
1. Creating several projects with separate domains.
To make a bilingual website, create two projects (Business paid plan is required). It is usually easier to create a complete project in one language and then copy and translate it.
Set up the header for both projects adding either the ME204 menu block, or one of the universal menus: ME301, ME302, ME303, or one of the hamburger menus: ME401, ME402, ME304. Open the Content panel and add the languages and the links to the projects.
Menu blocks mentioned above are useful for bilingual websites. If you need to have more than 2 languages, set up a dropdown menu http://help.tilda.ws/menu#two-levels
2. Creating several pages in different languages within a single website.
If you have a single page website and do not need a header (i.e. elements visible on all pages), you can create different versions of a page within one website (available on Free, Personal and Business plans). Set up two pages in different languages. Add a menu block to both. Use either the ME204 menu block, or one of the universal menus: ME301, ME302, ME303, or one of the hamburger menus: ME401, ME402, ME304. Open the Content panel of the block, add the languages and the links to the pages.