I'm thinking he means adding something to the ingame HUD, in which case you would have to go into mission editor and edit the corresponding gui.
I mean like in the city rpg mod where the hunger bar and stuff is
commandtoclient(%client, 'bottomprint', "Your message here", duration in seconds);
fsdffs nohttp://forum.blockland.us/index.php?topic=174198.msg4508233#msg4508233