You can download the Splice Create installer from this webpage: https://splice.com/create
Note: Create is only compatible with macOS 12+ at this time. Windows and web versions are coming soon.
After downloading:
Navigate to your Mac downloads folder and run the installer (SpliceCreate-Installer.pkg).
Follow the onscreen steps to complete the installation.
Create.app will be automatically added to your Applications folder after the installation is complete.