As the title says; How do i use infodecals and overlays? Atm, none of them show up in-game.
EDIT: Noticed that if you google "infodecal tutorial", this thread shows up as 3rd or something. So lets link to a solution/give a nice explanation for future visitors.
You still need help with the decals and overlays? Well, even if not, I write it here for the future.
I think that you used the enity-menu to select for example the infodecals, then you clicked on the 3d-view to place them. Nothing's wrong at all, but you should maybe try to use the menu, which is normally on the left border of hammer. They are the 8th and 9th. If you place them, make sure that you have all the faces, they touch selected under "Brush Faces". If it touches multiple, click on "Pick..." and hold down ctrl, while clicking on all the faces.
Hope this helps you.