In general, we reccommend not to show row labels; the less busy a chart is, the better. And one can ponder about how useful row labels actually are for ticket buyers.
However, if you want to show row labels, you can. Simply head over to Designer and enable them from there:
Select the row or rows you want to show the row labels for
click one or both of the Position buttons
if need be, publish the chart.
And that's it! Your seating chart will now display the row labels.