Select the cell below the rows and to the right of the columns you want to keep visible
Go to the View tab
Click Freeze Panes
Select Freeze Panes from the dropdown
To freeze multiple rows, select the row below the last row you want frozen
To freeze multiple columns, select the column to the right of the last column you want frozen
To freeze both rows and columns, select the cell at the intersection of the desired frozen rows and columns
To unfreeze panes, go to View, click Freeze Panes, then select Unfreeze Panes