Before adding content to your email you must first fill it with rows to create your desired layout.
To get started select on the 'Rows' tab and you will be presented with different row layouts ⬇️
On the 'Content' tab you can drag and drop the content types you would like to populate your rows with ⬇️
You can duplicate or delete the row by clicking on the outer area ⬇️
On the left hand side you can drag the row in order to change it's position within your email ⬇️