Help text should be input for all fields in your files. There is no help text at the file level.
A standard HELP text form should be set up and used as the basis for all field level HELP text. Use of attributes and $$ substitution variables can vastly reduce the amount of keying required to input a field's HELP text.
Refer to Messages and the Help Key in the LANSA for i User Guide to start learning about the LANSA Help facilities on IBM i.