With a text added to the design area. There are some options for it. To enable options, just click on the text and see the top toolbar as below:
This option allows you switch to another font family easily.
This tool allows you change the font-size, line-height even text content
There are some text effects on Editor. To access it, just select a text and choose Text Effect icon.
Check out text effect tutorial here
These options help you change text style as bold, underline, italic or text-align as well.