This is a tool I've notoriously have had to replace many times on my guides and thankfully with this tool, that will no longer be the case.
To use the tool, select the tiles you have in game using the tiles at the top of the tool panel. Each selection will appear in the Selected Tiles section.
If you make a mistake, you can click the tile in the Selected Tiles section to remove it. Once all 14 tiles have been added, it will attempt to find a solution.
If one is found, then it will flip to the Solution display and show you how to organize the Mahjong tiles in game to complete the step.
Place the tiles in this orientation and the step will be completed!