Take a look at bug-add.tcl in bugtracker for one example.
http://cvs.openacs.org/cvs/openacs-4/packages/bug-tracker/www/bug-add.tcl?rev=1.12&view=auto
In which context exactly are you looking for what to do? Is it a new script or an existing one? There are certain things to consider when switching an existing form builder element to use richtext, one thing is the need for an additional "format" column in the datamodel so that the chosen format can persist and the other thing is the beloved upgrade scripts.
