Using an answer from your application at the job interview

Yes. It's ok to use an example from your application form at a job interview. Try not to parrot your answer though! Talk about it like you haven't learned it off by heart and sound interested in what you are saying.

However, always have a backup example for every competency. That answer on the form might not answer every question asked about that competency. And an interviewer might ask for a different example than the one on the form, so it's best to be prepared for that.