To create a drop down list for an entire column in Excel, you can use the "Fill Handle" feature. Here are the steps:

1. Select the cell that contains the drop down list you created using the data validation method.
2. Click on the "Fill Handle" (the small square at the bottom right corner of the selected cell) and drag it down to the last cell in the column where you want the drop down list to appear.
3. Release the mouse button and select "Fill Series" from the options that appear.

This will copy the drop down list to all the cells in the column. Now, when you click on any cell in that column, you will see the drop down list.

Note: Make sure that the cell containing the drop down list is in the same row as the other cells where you want the list to appear. If the cell is not in the same row, Excel will not be able to copy the list to the other cells.