To view your top customers:

Step 1: Visit Dashboard > Marketing.
Step 2: Expand the Top Customers Report.
Step 3: Select the date range for which you want to view this report from the dropdown on the right. You can also filter this report by customer groups as well as print and export it to CSV.

Note: To export and download the report, simply click the export button on the top right. Access and download your exported report for a period of 7 days by selecting Saved Reports.