Don't have a Zendesk Chat account yet? Go to https://www.zendesk.com/chat/ to sign up and create one.

Zendesk Chat login: https://www.zendesk.com/login/
Enter you subdomain and click on 'Sign in'.
You'll be redirected to the login screen. Enter your email address and password en sign in.

You'll now be redirected to your Zendesk Chat dashboard.

Go to Settings > Widget in the navigation menu on the left
Copy the widget code below: