how it works is the DLC in fallout games comes in the form of a mission like a radion beacon has been picked up or you get a message from a stranger saying go here and its a map marker.
IF this doesnt happen when you boot up the game witht he desktop EXE it should open a box and in this box there should be the following.
hit data and another window will open in this window you can tick the content you want to load. like DLC and also load loose content. tick them all. BUT if they are not in this box this you DLC isnt installed and you need to explore the disc and install each DLC with the exe in each folder for it.
any problems let me know