Simply press the tilde(`) key on your keyboard to open up the Console. I use an English Keyboard so for Keyboards in other languages I am not sure what the key would be.

Make sure you paste the code exactly, such as "GiveItem(xx)" Without quotes and "x" being the item number.

Another thing, you can only spawn one item at a time. However once you use a code it will pop up on a window to the right. Simply click the code to spawn another. If you are already carrying a max number of items in your hands(4) you have to exit console, switch inventory slots, reopen console, then spawn another four.

• GiveItem(15) = Cherry Wood
  
• GiveItem(22) = Fir Wood
  
• GiveItem(37) = Oak Wood
  
• GiveItem(44) = Pine Wood
  
• GiveItem(49) = Rose Wood
  
• GiveItem(68) = Walnut Wood

• GiveItem(1) = Aged Copper
  
• GiveItem(2) = Aluminum
  
• GiveItem(11) = Iron
  
• GiveItem(16) = Copper
  
• GiveItem(25) = Gold
  
• GiveItem(56) = Silver

• GiveItem(10) = Black Marble
  
• GiveItem(12) = Brown Granite
  
• GiveItem(13) = Light Terrazite
  
• GiveItem(27) = Green Onyx
  
• GiveItem(35) = White Marble
  
• GiveItem(48) = Rose Quartz

• GiveItem(94) = Blue Fabric
  
• GiveItem(102) = Green Fabric
  
• GiveItem(103) = Red Fabric
  
• GiveItem(104) = Yellow Fabric
  
• GiveItem(112) = Black Fabric
  
• GiveItem(113) = Purple Fabric

• GiveItem(108) = Wood Token
  
• GiveItem(109) = Metal Token
  
• GiveItem(110) = Stone Token
  
• GiveItem(111) = Fabric Token

• GiveItem(82) = Yellow Pumpkin
  
• GiveItem(83) = Green Pumpkin
  
• GiveItem(84) = Onion
  
• GiveItem(85) = Carrot
  
• GiveItem(86) = Potato
  
• GiveItem(87) = Turnip
  
• GiveItem(92) = Apple
  
• GiveItem(93) = Peach
  
• GiveItem(96) = Hot Cocoa
  
• GiveItem(97) = Steamy Coffee
  
• GiveItem(98) = Rhubarb Pie
  
• GiveItem(101) = Beet
  
• GiveItem(106) = Green Fish
  
• GiveItem(107)= Purple Fish

This list may be incomplete. As far as I know these are all the resources in the game used for crafting. I don't even want to begin to dig into codes for furniture or other objects as the codes can get extremely high and complex.

If anyone wants to share any item codes they found, please feel free to comment and I'll add it to the list!