and the Delete the fileset button 
and the Shortcut menu to access Fileset Properties.A fileset is displayed on its own tab in the Filesets window. You can use the Add a new fileset button and the Delete the fileset button and the Shortcut menu to access Fileset Properties.
Or you can use the actions offered by the Fileset menu.
To create a new fileset:
On the Fileset menu, click New Fileset to display the Fileset Properties dialog box.
Enter the Name of the new fileset or accept the default.
Enter the Time Offset details or accept the default.
Multiple filesets are required where:
Data from one echosounder with multiple variables are stored in different files, for example, BI500 data for two or more frequencies; or
Two or more echosounders are operated at the one time; for example, Simrad EY500 and BioSonics DT4000 echosounders operated simultaneously.
You wish to add a Text data file to the EV file.
To delete a fileset:
Ensure the fileset you wish to delete is active.
On the Fileset menu, click Delete Fileset.
Note: Fileset1 cannot be deleted.