You might be expecting a simple "Installer" app, but OpenCore is different. It is a collection of files that you must configure manually. Once you extract the zip, you will see several folders. The most important ones are:
: Look for the OpenCore-Patcher.pkg or the standalone app.
To obtain the official, latest release of the OpenCore bootloader.
: Specifically for older Apple Mac hardware. It simplifies the process by providing a GUI application that handles the driver patching automatically.