Click on the « Block » tab on the left.
In the display menu, you can choose the block you need to build your newsletter.
Select the block and click on the « Add » button display on rollover.
The bloc will be add in the newsletter under the last selected block.
You can also drag and drop the block in the right place in the middle of the screen.
You can move, duplicate, delete the blocks in the design area.
When you click on a block in the middle of the screen, here are the different button display.
1 : Drag and drop
2 : Up
3 : Down
4 : Version of the block update langs set en=one block can have many versions)
5 : Duplicate
6 : Delete