I want to apply different styles to the text in my post. How can I do that?

Beyond using the toolbar in the Post Edit screen (in Visual mode), if you're comfortable editing HTML and use some custom Largo classes to style your text.

You can use <p> to call out the first paragraph in a post:

You can also add class="intro" to a div for the same effect.

To make text smaller, you can add these classes:

<p class="small">

<p class="xsmall">

For more see the Largo User's Guide/Style Guide.