Data
-> Data Tools -> Data Validation
Validation Settings
The default
value for a cell is Any Value. Validation criteria can restrict data
entry to Whole numbers, decimals, Dates or Time.
For our
example, select List from the options.
After you
Allow the List, you need to identify the data Source. Our
list is on the Accounts spreadsheet. We named that range: clients.
Click in the
Source box and type: =clients