I got something completely legal i need to burn to a disc, though i only have a bin file, how do you go about writing a cue sheet?

Go find a cuesheet for something else, open it up in your favorite text editor, and replace the things that need obvious replacement. IIRC you only need to change one or two fields and it's really easy to tell which ones they are.

If you're writing a cuesheet for something more complicated than a simple data CD image (like an audio CD track layout) check out teh Wiki's page on cuesheets and look at the external references too:

http://en.wikipedia.org/wiki/Cuesheet

A program like this to convert to iso:
http://www.weethet.nl/english/cdrw_bintoiso.php

(No warrenty, guarentee, etc on that program there, I haven't tried it)