Save Report As PDF Or Spreadsheet

On the Report Preview screen, click the Printer icon. On the Print dialog box, check the option Print to File.

You can choose the file type via the Type drop down. XLS Data File and XLS Report File are the Excel spreadsheet equivalents.

Click the [...] button on the bottom right to choose a file save location.

I saved my report as a spreadsheet but it came out blank. 
This is due to how the report is created. if you use the XLS Data File type with a Summary report, the spreadsheet will show no records. This is due to the XLS Data File format only showing 'detailed' records, which are hidden for summary reports. There is not currently a way to force XLS Data File to show summary record items. However, you can try generating as a PDF or as the XLS Report File type and then copy/paste information to a blank spreadsheet as needed.