First, install the extension into your VS Code instance and make sure it's enabled.
Make sure the /bin/ folder of your mCRL2 installation is either available from your PATH or configured in the extension settings.
Open the directory that contains your .mcrl2 files and optionally your properties (in subdirectories).
Use any of the provided run-options at the top right of the editor window, or alternatively, use the keybindings described below.
Keybindings
F4: Parses the specification. F5: Shows the LTS Graph. F6: Simulates the LTS. F7: Verifies all found properties.