You can have one to three arguments in the VirtualXL() call.
If you have only one, its the file name (as you have):
CREATE VIRTUAL TABLE MyVirtualTable1 USING VirtualXL("C:\Users\[path-to-file]\TestExcelSheet.xls");
If you have two, the first is the file name, and the second is the worksheet index (since Excel supports multiple sheets within the file). If you don't specify that worksheet name (i.e. you just specify the filename), its always the first worksheet. Note that this is zero-based (so the first worksheet is 0, second worksheet is 1, third worksheet is 2, and so on)
CREATE VIRTUAL TABLE MyVirtualTable1 USING VirtualXL("C:\Users\[path-to-file]\TestExcelSheet.xls", 2);
If you have three, the first two arguments are for the two argument case, and the third argument specifies whether the first line is titles (1) or not (anything else).
CREATE VIRTUAL TABLE MyVirtualTable1 USING VirtualXL("C:\Users\[path-to-file]\TestExcelSheet.xls", 2, 1);
For exact code, see https://www.gaia-gis.it/fossil/libspatialite/artifact/48852afbf76861da31691fe230dc73e561682e24 and look for vXL_create
You also might find the new ImportXLS() function useful if you'd prefer to import rather than work using virtual tables (i.e. copy rather than work on the .xls). See http://www.gaia-gis.it/gaia-sins/spatialite-sql-4.3.0.html for the syntax, which is very similar to the above.