Here are instructions for both Tomcat and JBoss packages.
Add the following to the $PLATFORM_TOMCAT_HOME/gatein/conf/exo.properties file to have the following lines 
(see Configuration overview for this file):
#SSO 
gatein.sso.enabled=true
gatein.sso.callback.enabled=${gatein.sso.enabled}
gatein.sso.login.module.enabled=${gatein.sso.enabled}
gatein.sso.login.module.class=org.gatein.sso.agent.login.SSOLoginModule
gatein.sso.server.url=http://localhost:8888/openam
gatein.sso.openam.realm=exo
gatein.sso.portal.url=http://localhost:8080
gatein.sso.filter.logout.class=org.gatein.sso.agent.filter.OpenSSOLogoutFilter
gatein.sso.filter.logout.url=${gatein.sso.server.url}/UI/Logout
gatein.sso.filter.login.sso.url=${gatein.sso.server.url}/UI/Login?realm=${gatein.sso.openam.realm}&goto=${gatein.sso.portal.url}/@@portal.container.name@@/initiatessologinIn which:
gatein.sso.server.url (= http://localhost:8888/openam in this example) is the URL of your OpenAM web context.
gatein.sso.portal.url (= http://localhost:8080 in this example) is the URL of your eXo Platform server.
gatein.sso.openam.realm (= exo in this example) is the realm created in previous steps.
			Edit the $PLATFORM_JBOSS_HOME/standalone/configuration/gatein/exo.properties file to have the following lines 
			(see Configuration overview for this file):
		
# SSO
gatein.sso.enabled=true
gatein.sso.callback.enabled=${gatein.sso.enabled}
gatein.sso.login.module.enabled=${gatein.sso.enabled}
gatein.sso.login.module.class=org.gatein.sso.agent.login.SSOLoginModule
gatein.sso.server.url=http://localhost:8888/openam
gatein.sso.openam.realm=exo
gatein.sso.portal.url=http://localhost:8080
gatein.sso.filter.logout.class=org.gatein.sso.agent.filter.OpenSSOLogoutFilter
gatein.sso.filter.logout.url=${gatein.sso.server.url}/UI/Logout
gatein.sso.filter.login.sso.url=${gatein.sso.server.url}/UI/Login?realm=${gatein.sso.openam.realm}&goto=${gatein.sso.portal.url}/@@portal.container.name@@/initiatessologinIn which:
					gatein.sso.server.url (= http://localhost:8888/openam in this example) is the URL of your OpenAM web context.
				
					gatein.sso.portal.url (= http://localhost:8080 in this example) is the URL of your eXo Platform server.
				
					gatein.sso.openam.realm (= gatein in this example) is the realm created in previous steps.
				
Uncomment the below login module in $PLATFORM_JBOSS_HOME/standalone/configuration/standalone-exo.xml, 
then change ${gatein.sso.login.module.enabled} and ${gatein.sso.login.module.class}
into #{gatein.sso.login.module.enabled} and #{gatein.sso.login.module.class} respectively.
<login-module code="org.gatein.sso.integration.SSODelegateLoginModule" flag="required">
<module-option name="enabled" value="#{gatein.sso.login.module.enabled}"/>
<module-option name="delegateClassName" value="#{gatein.sso.login.module.class}"/>
<module-option name="portalContainerName" value="portal"/>
<module-option name="realmName" value="gatein-domain"/>
<module-option name="password-stacking" value="useFirstPass"/>
</login-module>
After configuring the eXo Platform server, move to the next section for testing.