theme switching

Hi

From the Accesibility page it sounds like individuals can choose their own theme.

Theme Switching

Theme Builder 3.0 and above support end-user theme switching allowing individuals to instantly switch to a more accessible view of your wiki, for example you can provide high-contrast or large-text layouts.

Am I reading this right? If so how can a user select their own theme? I can't find any documentation on how an individual can do so.

This would be huge and the long sought holy grail of giving views for beginners versus power users.

thanks!
Brendan