You can add a section to one row which has two columns. That will follow the Red line you have mentioned in the screenshot.
Then you can use the Image Element for the left column.
For the right column, you can drag the Classic Featured list element and also right below that you can drag the button element. So in this particular case, you do not need additional Rows/Columns nested.
But if you want to have the nested row/column. You need to go to X > Global Blocks and add the nested row/column with proper elements inside them there. For more information click here. After that, you can use the Global Block element in the builder itself to add the nested items inside the builder itself.
I suggest that you read the Cornerstone/Content Builder section of our KB articles overview.