WYSYWIG = What You See Is What You Get
Wagn uses the customizable TinyMCE editor for user-friendly editing of rich text, so that users don't have to learn a lot of markup.
Our *tinyMCE card here on wagn.org has:
theme_advanced_buttons1 : "formatselect,bold,italic,"
The "formatselect" is what makes the menu appear in our edit toolbar, and the "bold" and "italic" puts the corresponding buttons there as well:
There's also a line with:
theme_advanced_blockformats : "p,h1,h2,pre",
...which is why the menu offers Paragraph, Heading 1, Heading 2, and Preformatted.
Simply edit the *tinyMCE card to your heart's content (on your Wagn — here, you can only edit it if you have the role of Developers). See the TinyMCE configuration documentation and especially their button documentation to learn about everything that you can do.