If you already have Tidal installed, you can upgrade it with the following commands in a terminal window:
cabal update cabal install tidal
You will also need to upgrade your editor plugin/extension. In atom, you can do this via preferences > updates.
Installing from scratch
Note: the documentation here recommends the Atom editor for typing Tidal code. If you wish to use a different editor, take a look at the List of tidal editors.
Choose your operating system: