To launch MySQL Workbench on macOS, open the Applications folder in the Finder, then double-click MySQL Workbench.

It is also possible to start MySQL Workbench from the command line:

$> open MySQLWorkbench.app [options] [model_file]

Specifying options, a model file, or both is optional. For example:

$> /Applications/MySQLWorkbench.app/Contents/MacOS/MySQLWorkbench

To show the available command-line options:

$> /Applications/MySQLWorkbench.app/Contents/MacOS/MySQLWorkbench --help