The following description relates primarily to Word 2013, but it mostly applies to newer versions of Word, too.
To access the settings, set the document language to Finnish and open Word Options, then select Proofing. You can then see the dropdown menu “Writing Style”, with the button “Settings” on the right of it. At the simplest, you can just use the dropdown to select one of the following:
It is usually best to start with Tiukka and drop some requirements if they turn out to be unsuitable for your style or purposes. Instead of just switching to Normaali or even Vapaa, consider clicking on Settings and just turning off (or on) the individual settings. The Settings button opens the Grammar Settings window with a set of checkboxes. You can this way change the meanings of Tiukka, Normaali, and Vapaa in your copy of Word. You can alternatively select the fourth option in the dropdown menu, Omat asetukset (Own settings), and tune them as desired. The button Reset All sets all the options to their default values, for the writing style being used.