Just click on the columns you want to protect. Right click and select format cells.
On the protection tab check the box LOCKED. Then ok. Next step is to click the REVIEW tab on the top and in the CHANGES section select PROTECT SHEET. In this pop-up window make sure the protect worksheet and contents box is checked. Set a password to unprotect the sheet and allow changes to be made. Then you can select other protection options. When done click OK and save your worksheet.