Think of seasoning like you would for a cast iron skillet.
Does the metal inside the smoker look shiny and new or does it look black? It's only not seasoned if you see a lot of shiny metal.
All I'd suggest is to throughly clean the shelves, if they've been sitting around.
Cover the V shape hood over the heat source with foil, line the bottom of the smoker with foil.
Do a "seasoning" smoke by placing 4 or 5 chunks of wood in the smoker, set it on 250 and let it smoke until there's no more smoke.
Even it it's already seasoned, this will ensure.
You shouldn't see smoke coming out anywhere except the top vent hole. Although a very small amount may come out around the door, depending on the shape of your smoker.
Smokin'