unified sdk chat is not working

I have added unified sdk and using your example. But my chat is not connecting to an agent. I am using your unified sample from https://github.com/zendesk/ios_sdk_demo_apps

In this example, there is a line

Chat.initialize(accountKey: accountKey) 

In this its asking for account key But. I am unable to generate account key.

Can you please help what is this account key and how I will generate it.