If you applied online you should have got an acknowledgement email straight away as a receipt of application. You should receive another email within the next month or two about the next stage of the application process - yes it can take months for them to get back to you - then you will have to take the "exam" usually within two weeks of this notification. Then wait another month or two for your "results" then hope for the best after that.
Q How many people usually apply for this position?
A Thousands and thousands - many just apply for the sake of it. Some for the experience of doing the exam. Some like the sound of the Civil Service and even some who actually want the job.
BB