The app doesn't work out of the box – it must be configured before, not to mention the projects, issues and workflows configuring required for the relevant process tuning. The CRM app settings are located at Jira Administration → CRM and are accessible for a user with Jira Admin rights.
The app provides some default settings – they described in the relevant sections of current documentation.
You will also need to add a CRM superuser – the "technical" user with access to Jira to perform actions in the system.