For details on how to import products from a flat file refer to :
http://www.miva.com/docs/merchant/howto41/MM1014.pdf .

Recently I came across a problem where when I imported products from a text file for a customer within miva admin it worked but the same file did not for the customer. I was using windows and the customer was using a mac his files were being shown as one record where as mine were shown as deifferent records.

The customer found out the following:

The problem is miva likes only a DOS LINE BREAK OR CARRIAGE RETURN and does not like a UNIX or MAC LINE BREAK OR CARRIAGE RETURN.

Mac user can get BBEdit editor tahtw ill elt them save a text file in dos mode and that should work in miva admin properly.

Yes, BBEdit is pretty much *the* text editor for Mac users. The lite version is available for download here:
ftp://ftp.barebones.com/pub/freeware/BBEdit_Lite_612.smi.hqx

This .hqx file will need to be expanded with a program such as Stuffit Expander. It includes a version for both OS X and the classic Mac OS. I believe the classic version will work back to version 8.1, but I can't find definitive information on Bare Bones' website.

To change the line break format once you've got your file open in BBEdit, simply drop down the third little menu in the document's toolbar(the one that looks somewhat like a file), and in the list you will see "Macintosh; Unix; DOS" in the list. Following Jitu's instructions, select DOS, save your file, and upload it again. Miva should now be able to import it.