To protect specific cells and ranges in an Excel sheet, there are a few steps to take:

1. Select the range of cells you’d like to protect.
2. Choose the ‘Format Cells’ option from the drop-down menu.
3. Go to the ‘Protection’ tab and check the ‘Locked’ option.
4. Go to the ‘Review’ tab and click on the ‘Protect Sheet’ button.
5. Enter a password (optional) and click ‘OK’.