To format text as bold, make sure you are in editing mode (the screen will say "Draft" in the upper left corner), and select some text:
Using a Keyboard Shortcut:
- Press ⌘ + B / Ctrl + B Bold
Using the Text Toolbar:
When you highlight text and wait, the text toolbar appears.
Click on "B" in the toolbar to make the selected text bold.
The "B" will turn green, and your text is now bold.
Click on "B" again to remove the bold effect.