In a post apocalypse you must venture out of your base, donning your oxygen mask, to go and search for supplies and cure the infected.

Move with WASD, shoot by clicking on the enemies, open your inventory with i and craft supplies at the crafting table.
You can use some items from the inventory my selecting them
Crafting:
Scrap Metal + Gunpowder = Ammo
Can + Plant = Food
Plant + Slug = Medkit
Medkit + Food = Cure