First, click in the cell directly below and to the right of the section that you want to freeze.

Then, go to Window >> Freeze Panes.

Dark lines appear to the left and above the selected cell. These lines show the frozen area.

You should be able to scroll through your data while still being able to see your column and/or row titles.

To unfreeze, just go back to Window >> Unfreeze Panes.

The first thing you need to do is Unlock any cells that you want the users to be able to edit (you don't need to worry about this if you want to protect the whole worksheet).

Simply select the cell or cells that you want to unlock, then go to Format >> Cells >> Protection and uncheck the Locked button.

To Protect the worksheet, go to Tools >> Protection >> Protect Sheet.

In the Protect Sheet window, you can add a password (leave it blank if you don't want a password).

You can also designate certain actions that the users are allowed to take on the protected areas.

To remove the protection, go to Tools >> Protection >> Unprotect Sheet (you'll have to know the password if there is one).