How did you come to know about the vacancy in your company? Was it through company's general notice board or ad in newspaper or ad in job portal? Whatever may be the means of communication to you, you can give reference of it and apply for the post.
In your application, no need to attached your CV. When you acquired your current as such you must have submitted your CV and HR must be in possession of that copy.
Route your application through your HOD. If HOD hands over the application to HR then well and good otherwise, with HOD's remark on your application, hand it over to the HR.
More than process of submitting the application, the important question is about suitability for the post. Selecting authority could ask you about this question and you are expected to give a credible answer.
17th November 2018 From India, Bangalore