This is an after deckhouse for the big 1/144th scale Revell Fletcher-class destroyer model. It specifically represents the USS Heerman but can be used to represent other Bethlehem-built Fletchers and others similarly modified as the war went on. Please check your references to ensure that this deckhouse is correct for the ship that you are modeling, as there were many differences and ships often went through a number of refits and their configurations could change often.
Ammunition racks were not included in the interior of the splinter shielding because these arrangements were so individual from ship to ship, and because of current printing limitations; freestanding details just can’t be printed that small at the present time. The modeler may wish to represent these details with photoetch or by scratchbuilding ammunition racks of his own. However, a 40mm barrel locker is included, as is a nicely detailed base for the modeler supplied 40mm Bofors. Simply remove the parts from the sprue using nippers or similar, clean up with a nice sanding stick, and install.
Its probably best to clean the parts before painting by soaking them in lukewarm soapy water and then scrubbing them CAREFULLY with a very soft toothbrush. Remember, these parts are fragile so go slowly and gently. Allow to dry. The modeler can use whichever version of photoetched door (not included) was best for his ship, gluing it over the door opening. Again, check your references. Prime with your favorite acrylic primer using regular hobby paints. You may wish to consider painting the interior of the deckhouse to reduce light transfer through the part and make it more opaque. Acrylic paints are usually best for painting these printed parts as solvent based enamels have been known to attack them. I personally have not experienced this, but in the name of full disclosure others have, so its recommended that you use acrylic paints just to be safe.
The part does not have deck camber, so you may wish to sand the undersides slightly both to give some “teeth” for the glue to bite into, but also to better contour the deckhouse to the kit’s deck. Depending upon how “tightly” the modeler builds up the model’s various assemblies the camber can vary slightly, and a part with camber may not fit properly.