One problem with the file layout editor in Application Designer is that you cannot see the fields in order in which they appear in the file. For XML files, this does not matter, but for CSV files or flat files, the order is very important, especially in troubleshooting.
Here is some SQL that will show you the fields in the correct order (Just replace the <File Layout Here>):
SELECT * FROM PSFLDFIELDDEFN WHERE FLDDEFNNAME = '<file Layout Name>' ORDER BY FLDSTART
how to import excel files in to peoplesoft
PeopleSoft has a tool called Excel To CI, which allows you to load data from an Excel spreadsheet into a PeopleSoft Component Interface. You can read more about it in PeopleBooks: https://peoplebooks.uta.edu/PSOL/pt846books/eng/psbooks/tcpi/book.htm?File=tcpi/htm/tcpi08.htm%23H4015
Another option is using CSV files. In Excel, you can save your spreadsheet as a CSV file with the Save As option. Then, File Layouts have a CSV file type option. Open the properties for a file layout to change it to a CSV file type.