The first step to create your map consists in selecting a scenario. Scenarii represent different graphical methods to display your data on the final map. Some of them allow you to work with a single data (Quantitative Filling, Proportional Symbols, etc.) and the others are designed to display or compare multiple data (Pies, Charts, Filling with Proportional Symbols, Portions, etc.)
As we want to compare two numeric data on the map (number of customers and customers rate), click on the "Filling with Proportional Symbols" scenario in the dialog box, then click on "OK" to reach the next step.