What do I say about why I left my last job?

I have an interview next week and I am unsure how to explain why I left my last job as a security officer. This is my first time dealing with any of this. I also do not want to seem like a risk. Do they ask follow-ups?

Practise it out loud with a friend. Mine felt natural after the third try.

Say it plainly and move on to what you can do. Interviewers usually move on if you do.