There are two main ways to copy data validation rules to other cells in Excel:

Method 1: Using Paste Special

1. Select the cell with the data validation rule: Click on the cell that has the data validation rule you want to copy.
2. Copy the cell: Press Ctrl + C (or right-click and choose "Copy") to copy the cell.
3. Select the target cells: Highlight the cells where you want to apply the same data validation rule.
4. Paste Special: Right-click on the selected cells and choose "Paste Special."
5. Select Validation only: In the "Paste Special" window, under "Paste options," choose "Validation" only. You can uncheck other options like "Formats" or "Values" if you don't want them copied.
6. Click OK: Click "OK" to apply the data validation rule from the copied cell to the selected cells.

Method 2: Extending the validation to adjacent cells

1. Select multiple cells (optional): If you want to apply the rule to a contiguous range, highlight the cells that already have the validation and the cells you want to add it to. You can hold Ctrl while clicking to select non-adjacent cells.
2. Go to Data Validation: Navigate to the "Data" tab on the ribbon. Click on "Data Validation" in the "Data Tools" group.
3. Extend the validation (if prompted): If you have multiple cells selected, Excel will prompt you with a message like "The selected cells contain different validation rules. Do you want to extend the validation rules from the first cell to all selected cells?" Click "Yes" to apply the existing validation rule to all selected cells.

Using either method will efficiently copy the data validation rule to your desired cells, ensuring consistent data entry across your spreadsheet.