Once you have customised and run your report, you can export it to a .CSV file.
From the report page, click Export Detail.
From Export File Format, select Comma Delimited .csv.
NOTE: always use .csv format as this will put the data into Excel without formatting.
Click Export. This will export the report in the format you selected.
Your report will be exported to Excel in .csv format. Depending on your browser, you may find the exported report at the bottom left or top right. Click on it to open the report.
NOTE: remember to use Save As when you want to save this report. Give it a name and change the file format to .xlsx.