[keycloak-user] Examples of server that implements OIDC Protocol? Questions about Linking accounts

Hello I'm looking to build an application ( identity provider) that will have user accounts. Users then should then be able to link their account to a parent account, and I would like to use keycloak for this. I have been reading http://www.keycloak.org/docs/3.1/server_development/topics/identity-broke... and see that this is possible. I have a few questions. On the docs it says: How does an application login as a user? Does this mean the user must be logged into the Identity provider application? Am I correct in assuming the Identity Provider application needs to implement the OIDC Protocol? Is this something Keycloak can do? Are there any examples of this? Thanks and regards Anton