First, you setup the board with the cities (don't know the english name) and place goods randomly and face down on every spot (depending on player count). ALL goods that are left over will be sorted (cereal, cheese, wine, etc.) and putted into the market in their respective piles.
How do i know how many goods go in the supply stacks...
All goods left over after placing them on ways and rivers on the "cities board"
And if you are playing with fewer than 4 players, then you will remove either 6 or 12 tiles at random from the game before you put the remaining tiles in the respective piles.