You can add a Row to a Form by opening the Main Form Definition window. Only users defined as System Admin, or a Full user with the specific module "admin" role, can access Main Form Definition.
In your selected sub-module you can click the Cogwheel icon to open the Main Form Definition window.
Adding a Row is as simple as clicking the “+” icon in the Main Form Definition window.
From here, you will be able to define how many columns you would like to have displayed in your row.