To open the console click on the console icon in the toolbar at the top.
An editor winod should appear and give you some advices. By rightclicking in the window you get the menu with the needed execution commands.
In oder to properly work there are some settings that have to be controlled. Just go in the preferences and search for the Console tab. If everything was installed properly, you will only need to set the path to fit to your GRASS installation, which is needed if you want to execute GRASS commands:
Here you will have to set GISBASE, the binary path and the libraries path, with additional libraries path addition for MACOSX systems. That done, you are ready to rumble.
The global GRASS database setting, which you found playing around in the tabs seen above can be overridden for every console session. This is done in the Runtime Preferences which pop up from the menu appeared by right-clicking.
The console mostly works with OpenMI based models and therefore has support for chaining models throught a timeline.