You need to pick a subset of the spreadsheet that is straight tabular data with no formulas, strip out everything else, "Save As CSV" and then it will work. The resulting file should have a set of fields separated by commas that is consistent from top to bottom with a field header as the top row. Your stuff is NOTHING like that.
Perhaps you can understand Splunk more by reading the documentation from Splunk as to what we can index :
Splunk cant read binary data without preprocessing or converting to human readable text.