How to sort posts by expiration?

I am an extreme WP beginner so please forgive my lack of knowledge in this area.

I have an events category and I want these posts to display in order of event dates expiring so the soonest expiring event is displayed first. I’m using the Post Expirator Plugin to expire the posts. However, the posts are being displayed by published date and I want to change this.

I am using Avenue theme. Here is the site.
http://www.kidstownsquare.com/

Is there an easy way to do this for a beginner? If there is a code, I need specifics on where to put it. Thanks in advance.