This is just like what you would do in MS Word or MS Works, highlight some text and select a different font. Before you get to change all the fonts on your page you need to realize that all computers don't have the same fonts. Their browser will only allow fonts installed on the local computer. For more information on how to use more fonts check backup font tip . This is the simplistic one, very self explanatory changing font size.
Nobody wants to go to a web page and it looking like ransom letter.