This stuff is in the Player's Handbook under the relevant feats (in this case, Craft Magic Arms and Armor), and also in the DMG sections on crafting magic items.
All magic items, regardless of type, take 1 day to enchant for every 1,000 gp of their market price. The market price for magic armor is 1,000 gp times the square of its enhancement bonus. That's just for the enchantment; it does not include the price of the armor itself. So enchanting armor to +2 takes 4 days.