Configuring Single signon

We have created a dicom viewer (web application) using dcm4chee-arc-light 5.13.2.mysql-secure. Now we are trying to integrate this in our HIS application. By clicking a link in HIS page, a viewer page should be opened with that particular series. The viewer application is bundled with a keycloak server for authentication purpose. In the viewer we have added the clients under Dcm4che realm.
HIS is also authenticated with a different keycloak server with realm name ABC. Both HIS and viewer are under different keycloak instances.
How do we integrate the viewer authentication in HIS keycloak instance to enable single signon? We have tried adding the dcm4che components as clients in HIS keycloak. But that is no working.

Thanks in advance.