the x factor 2013 auditions application forms on x factor website
good news, you can apply to the uk x factor again, the application forms are available for another year at this website address https://application.xfactor.tv/
it has the options for you to apply as a soloist or in a group, also all the details and rules are available at that address as well for those looking to apply for next years x factor 2013.
just a matter of taking a short amount of time to fill out the form and away you go. so far it does not look like the x factor usa 2013 application forms are up online but they will probably be just another week or so.