First make new blueprint from >> HUD << class.
then add DrawHUD event inside and you quite ready to go.
All text, boxes and bitmap draws are in HUD category.
My problem now is how to feed variables there, or how to make global variables readable by all blueprints, materials, and particle systems. That is still mystery for me.
ps.
Oh and point to your new blueprint_hud in dafaaults of gamemode_blueprint (or it was player_blueprint, one of core blueprints has dropdown box for setting hud class).