I hope you are using seam provided identity management, if it is the case you will have loggedin username already associated with session ( Identity.instance().getCredentials().getUsername()).
If you want to show other information to be displayed in every page then you must create one session scope class at startup where you build information and set it to some variable, access that variable whereever required.
You seem to have had quite a few very basic issues posted to these forums recently. Have you tried using seam-gen to create a functioning project, which includes login and sessions and conversations and all that jazz? It basically provides all the examples of things you've been asking for.