Return to the section with the row you wish to adjust by clicking on it in the Sections tab.
Click on the row letter. This will create a box around the row you are going to adjust.
Click on any of the white corner boxes and hold.
Drag the squares outward to add seats. Release when you have added all the additional seats you would like to see.
Drag the squares inward to remove seats. Release when you have all the seats you want removed gone.
Helpful Hints:
Eliminating all seats in the row will cause the row to disappear.
If you need to add a row back, find and select the section with the missing row in SECTIONS.
Click on the Add New Row button.
Note row H is gone in the image below.
Next you will be asked to name the row. I have chosen H.
Your newly generated row will appear after your last existing row in the section.
To move your newly added row, click on the row letter to highlight the row. Click on the center white circle to drag and drop the row in the position of your choosing.