Adding Drop Down Menus

[MARIE15]

I am trying to create a drop-down list for every cell in column "S", using data from cells in column "X". I have successfully created one for the first cell (S2), but how do I duplicate this menu for every cell in that column without having to laboriously create a new individual menu for each cell? I tried copy+pasting the list into each cell, but it copies the data from the first drop-down, which means whatever option is selected in that first one ends up being selected for all of them.