On the other hand, even though you say you are trying to import, from your description of what you got it may be that what you have actually done is open your Excel file in FM. In that case you will have been presented with the choice of importing the first row as data or using the first row as field names. If you used the first option, then the fields simply get named f1, f2, or something similar.
If you are really importing data from Excel you will have had to map the data from the spreadsheet file to the fields in your FM file, which is a process than can be as clear as mud. Sometimes it can be easier to simply open your Excel file in FM, a process that creates a new FM file, and then import from that.