Document how to download and install a local model

[deepcoder]

1st, thanks very much for this work!
I'm a bit of nube here.

The 'Get' button takes you to web page for the example, however chat-macOS instruction are not part of the options. And also where do you place the downloaded model for the "add +" option and where do the models go? Is there a way to configure where models are stored?

Thanks!