Easiest way is to use latexmk from repository
In texworks latexmk needs to be setup. A guide can be found here:
http://code.google.com/p/texworks/wiki/AdvancedTypesettingTools#latexmk
In texworks go to edit->preferences->typesetting
under “processing tools” add latexmk and add teh arguments found in the link above (repeates here):
-e
$pdflatex=q/pdflatex $synctexoption %O %S/
-pdf
$fullname
You need to add them one at a time