There are some great discussions on dogs and chickens here. If you type "train dog", for example, into the search bar you'll pull up quite a few of them and you'll get lots of tips there. Here's one to get you started:
https://www.backyardchickens.com/t/829562/training-teaching-a-dog-about-chickens/0_30
Start here and be consistent in your training and vigilance.