Click on it to see the options and select the language you are wanting to switch to. To switch languages quickly, in your system tray (bottom right-hand corner of your screen), there should be a MR sign which indicates your system default input language.
If you can't find Māori in the list, then in the same dialog box, scroll down to Maori (New Zealand), expand the Keyboard options and select Māori, then click OK.
Scroll down to English (New Zealand), expand the Keyboard options and click Show More.
Note: If it already says English (New Zealand)- Māori, then it's already set up.