You'll need to create three separate charts--one scatterplot and two histograms. Here are examples using superstore.
To make sure that everything aligns properly, you'll probably want to fix the axes so that each histogram matches the scatterplot.
Next, put them together on a dashboard and fiddle with the alignment and sizing until you get them just right.
Once the gridlines are aligned, you can start turning of some of the axes, etc. When you turn off the headers, you might once again encounter some alignment problems. I'd suggest using the padding options to realign.
I'm attaching my workbook in case you'd like to dig into it further.
Distribution.twbx 2.5 MB