Select the cell below the row(s) and to the right of the column(s) you want to keep visible
Go to the View tab
Click Freeze Panes
Click Freeze Panes from the dropdown
To freeze the top row, go to View, click Freeze Panes, then click Freeze Top Row
To freeze the first column, go to View, click Freeze Panes, then click Freeze First Column
To unfreeze panes, go to View, click Freeze Panes, then click Unfreeze Panes