Please note that there is no WSO2 Identity Server version that is currently compatible to be configured as the key manager of API Manager 2.0.0. The compatible version is expected to be released soon.
The Key Manager handles all clients, security and access token-related operations. For more information, see Key Manager.
To configure WSO2 Identity Server as the Key Manager of the API Manager, see Configuring WSO2 Identity Server as the Key Manager in WSO2 API Manager in the WSO2 Clustering documentation.