After installing and mounting the package, go to the package url and read the documentation (instalation of aspell and nsaspell). Their is a documentation of the nsaspell functions and the spellchecker functions as well.
In addition I put a litle java script into the doc dir. of the package wich you may include in the header of your master template.
And a patch for the forums package (to let it use the spellchecker ) , the patch is made with an older version of the forums package it may not work properly with newer ones.
The spellchecker skips html tags (including &code;) and numbers automaticly.
It is using a select box , to let the user chose a language (from all available) including None.
It is not implemented into the form builder jet, if you want the text from a text area be spellchecked , you would have to add a extra select box (to select a language) to the form , and then pass the text and the language to the spellchecker proc.