Warning: the Brew Cask has been renamed. If you used it previously as sdfcli, please untap the cask and uninstall:
brew untap limebox/netsuite
brew uninstall sdfcli
brew cask install caskroom/versions/java8 # Unless you already have Java 8 installed.
brew install limebox/netsuite/sdfsdk
The plugin is activated when a project is opened that has a .sdf or .sdfcli.json file in the root directory. So open a SDF project folder that contains a .sdf file.
If the Extension is activated, you should see a SDF button in the bottom left status bar. Click the button to open up the Select Environment inputs. This will generate a .sdfcli.json in your root directory of your project.
Fill in your environments that you want to be able to switch between inside of the extension inside of the .sdfcli.json.
Hit Ctrl+Shift+P for Windows, or Cmd+Shift+P to bring up the command palette again, and type SDF to see all the options.