[keycloak-user] Keycloak question - restricting client access to group of users

Hi all, I'm an un-experienced Keycloak user, using version 7.0.0. I've managed to setup Keycloak, and login at Gitlab(SAML) and Grafana(OAUTH) via Keycloak. This seems to work as it should. The issue i'm now facing is similar to this one<https://stackoverflow.com/questions/54305880/how-can-i-restrict-cl...;, how can I restrict client access to only one group of users, and how do I configure Keycloak to allow login through this client only, for both SAML and OAUTH. However, I can't work with the answers provided, they're unclear and or fuzzy. It's unclear for me what to do. Can someone explain to me, in an ELI5 fashion, how I need to configure keycloak in order to achieve this functionality? Thanks!