That's about as vague as a question can get!!

If I understand, you want to import 'to' FileMaker, from some other program,
(unspecified).  You should in the unspecified program, export in a file
format that can be read by FileMaker.

It will, at least read a comma delimited file, but this will be no good if
your data contains commas, such as addresses.  You could try tab-delimited
as a better option.  If you want to transfer formatting, etc then you should
aim for an export in HTML or XML