Skin: form for creating a story; Javascript

Hello,

as you may be aware, you can use simple javascript to insert predefined text or code into forms.

My question is: how do you do this i.e. in the form for creating a story? I would like to add a javascript snippet that i.e. inserts the text block in the open textbox - on click.

I do not know how to link the javascript snippet to the textbox, as there is no "form" tag used.