To make a dropdown first highlight the list you wish and give it a name
(anthing you want eg listX). Do this by going Insert>name>create.
After doing this go to the cell where you wish for the dropdown list to
appear, and go Data>Validation. When the box comes up, in the box next to
"allow:" secect "list". In the box below that says "source" type "=(your list
name).
For example "=ListX"
Your dropdown is then complete, so click ok.
hope this helps.