Your application could use any OpenID Connect client SDK, for instance AppAuth, but for now let's test it with a crafted link that upon a successful authentication will land on a mock dashboard page (http://mockbin.org/request)
The following crafted link emulate the call that your application would do to Keycloak to start the authentication flow.http://localhost:8080/auth/realms/my-realm/protocol/openid-connect/auth?client_id=my-client&redirect_uri=http://mockbin.org/request&response_mode=fragment&response_type=code&scope=openid
By clicking the above link, you will land on the default Keycloak login screen with your previously defined Identity Provider as an option. Click on it to login.
Congratulations! You integrated Keycloak IAM with your customised Login Page. The next step would be to configure an application to start using it here