Update README.md

README.md

@@ -53,12 +53,13 @@ Automatically, Tableau will sum all the values. So you can see now what is the t
 
 It's always important to have a sense of the distribution of a measure before you start analysing it.
 
-1. Click on `Height` (or `Weight`) from below "Measures", on the left-hand side of the window.
-2. Click on the histogram view on the right-hand side of the window.
+1. Make sure your "Columns" and "Rows" bars are empty by dragging-and-dropping their content away.
+2. Click on `Height` (or `Weight`) from below "Measures", on the left-hand side of the window.
+3. Click on the histogram view on the right-hand side of the window.
 
 ![Tableau join](img/histogram.png)
 
-3. Drag-and-drop `Gender` in the "Rows" bar.
+4. Drag-and-drop `Gender` in the "Rows" bar.
 
 Do you understan what you see?