Here's how to use data validation lists to restrict data entry options in Excel:

1. Select the Cells:

Choose the cell(s) where you want to restrict data entry using a dropdown list. You can select a single cell or a range of cells.

2. Access Data Validation:

Navigate to the "Data" tab on the Excel ribbon. In the "Data Tools" group, click "Data Validation."

3. Set Allow to List:

In the "Settings" tab of the Data Validation window, under "Allow," select "List" from the dropdown menu.

4. Define the Source:

This is where you tell Excel where to find the valid data options for the dropdown list. You have two choices:

- Directly Enter the List: In the "Source" box, type your options separated by commas. For example, "Apple,Orange,Banana."

- Reference the List Location: Click the small dropdown arrow next to the "Source" box and select the cell range containing your dropdown options (ensure this list is located elsewhere on your sheet or another sheet).

5. Additional Options (Optional):

- Ignore blank: Check this box if you want to allow users to leave the cell empty.
- In-cell dropdown: Check this box to display a small down arrow within the cell for easier access to the dropdown list.

6. Click OK:

Once you've defined your settings, click "OK" to close the Data Validation window.

Now, when you click on the selected cell(s), a dropdown list will appear displaying only the options you defined. Users can only choose from this list, preventing them from entering invalid data.