Select the cells you want to protect
Right-click and choose Format Cells
Go to the Protection tab
Check Locked
Click OK
Go to the Review tab
Click Protect Sheet
Set a password if desired
Choose the allowed actions
Click OK
Re-enter the password if prompted
To protect only specific cells, unlock the other cells first
Select the cells to remain editable
Open Format Cells
Clear the Locked checkbox
Protect the sheet again