You can do that in a several ways. The easiest way to add text is to use the text icon when you’re creating ShowMe lessons. Simply hit the text icon (Aa) on the top left icon bar. You can now type in the text you would like to add.
If you would like to use text or fonts not found in ShowMe:
Take a screenshot of the text on your computer and email the image to yourself, then save the attachment to your photo library. Alternatively, you can place the screenshot into your Dropbox and then insert it into ShowMe through ShowMe tools.