How do I put password to protect my entire Spreadsheet so data cannot be changed?

STEP#1: unlock all the cells that needs to be editable.

STEP#2: right-click anywhere in the sheet and select Format Cells and then go to the Protection tab and clear Locked

STEP#3: protect the worksheet by reviewing tab and click protect sheet, enter pasword.

go to the review and select protect workbook then put your password in a dialog box.

Go to review and press protect workbook

I can enter password to protect my Spread sheet using Protection Option in Tools.

1) Click Tools 2) select Protection, then Protect Sheet 3) Enter a password, Click OK 4) Re-enter password, 5) Click OK 

And ready to go.

To do this, click on File, then Save As. When the file-save window appears, type in your file name, then select the Tools drop down menu. From that menu, select General Options. This will enable you to password protect the entire workbook and prevent anyone else from opening it and viewing its contents