Select the cell below the row and to the right of the column you want to freeze
Go to the View tab
Click Freeze Panes
Choose Freeze Panes
To freeze only the top row, go to View tab and select Freeze Top Row
To freeze only the first column, go to View tab and select Freeze First Column
To unfreeze, go to View tab, click Freeze Panes, then select Unfreeze Panes