Add a new Zendesk Chat widget from your dashboard.
Select a preset widget from the list, or choose to Build your own widget.
Enter the subdomain of your Zendesk account. The subdomain can be found from your login details. For example, if you log in to Zendesk at https://mycompany.freshdesk.com, your subdomain is mycompany.
Click Connect via Zendesk on the connection panel. You'll now be asked to log into your Zendesk account, unless you're already logged in.
Finally, you'll be asked to give Geckoboard permission to access your account.
To connect a different Zendesk Chat account to the one you've already connected to Geckoboard, see connect multiple accounts to data sources.