If you are wanting to enlarge the size of text, select or highlight the
words/text you want and in the toolbar you should see the font being used and
the numeric size of the text.  You can enlarge your text that way. If that
toolbar isn't currently displayed, go to Format then Font.

If you're looking for something drastic, you can always create word art
which you can resize yourselt.  However, this will be an image and not text.

By adding extra letters?