You must apply online, via the Virgin Atlantic website. The pre-screening is directly from the online application. If that hurdle is successfully passed, you may be invited to interview. In the last recruiting round, there were exams - technical and other - and the interview could cover any topic relevant to the job. I seem to remember that the sim ride was dropped for a while and then reinstated, but a study of the Master Thread linked to in my last post will probably cover that.
In other words, it's a pretty standard airline recruiting procedure.