Here is the text from a post in the Chromebook help page
Install Android apps on your Chromebook
You can download and use Android apps on your Chromebook using the Google Play Store app.
Currently, the Google Play Store is only available for some Chromebooks. Learn which Chromebooks support Android apps.
Note: If you’re using your Chromebook at work or school, you might not be able to add the Google Play Store or download Android apps. For more information, contact your administrator.
Step 1: Get the Google Play Store app1. Update your Chromebook software
To get Android apps on your Chromebook, first update your Chromebook software. Your Chromebook must run Chrome OS version 53 and up.
2. Sign in to the Google Play StoreClick your account photo.Click Settings .In the "Google Play Store" section, turn on Enable Google Play Store on your Chromebook.
Note: If you don't see this option, your Chromebook doesn't work with Android apps. In the window that appears, click Get Started.You’ll be prompted to agree to the Terms of Service. When you’ve read and agreed, click Agree.To confirm your current Google account, click Sign In.You’ll see the Google Play Store app open. In the box that appears, click Accept.Step 2: Get Android apps
Now, you can find and download Android apps on your Chromebook.
Your Chromebook won’t automatically download the same Android apps as your phone or tablet, so you’ll need to download them again. Also, some apps don’t work with some Chromebooks, so you won’t be able to download them.