The Spectre toolchain can be installed in several ways. The easiest of which is to run the get.sh script from https://spectrelang.org/get.sh, or for Windows, the get.ps1 script from https://spectrelang.org/get.ps1.
The shortcut for doing this is simply running on POSIX systems (MacOS, Linux, etc...):
curl https://spectrelang.org/get.sh | shOr on Windows:
irm https://spectrelang.org/get.ps1 | iex