You can change the font size by clicking on the text, then choosing the resizing tool. There are 5 standard options for font size: Tiny, Small, Medium, Large, and Huge, and clicking on one will apply it to your scene:

There is also a slider option you can select if the 5 standard options aren't quite right. The slider lets your adjust the font size gradually, until the text looks perfect:

 

Did this answer your question?