Custom Text under avatar

[pooka]

I'm a little embarassed that I can't find it, but ...

What option under User CP do I click on to add custom text under my avatar on my posts? I search and search and search and found in the faq that there's a field called 'custom text' when I edit my profile, but it eludes me. Is this a 'premium' only feature or am I just blind?

Thanks in advance!