CMS Made Simple Forums

I'd like to make a simple change to the admin welcome message. From "Welcome: username" to "Welcome: First Name Last Name".

It seemed simple enough, but I'm missing something.

'.$this->cms->variables['username'] (current)

Changing username to first_name (as in DB) gives me a blank result. What would be the proper code for this?

Thanks in advance for your help.

Jeff T.