Importing WMI File – error message

Hi – please excuse me if there’s a simple solution but I’m pretty dumb when it comes to WordPress ;).

I’m trying to import old blogs/pages from another WP blog and keep getting this error:

File is empty. Please upload something more substantial. This error could also be caused by uploads being disabled in your php.ini or by post_max_size being defined as smaller than upload_max_filesize in php.ini.

I’ve ready about needing to change permissions but I have no idea how to do that or what it means.

Please please help!

Thanks so much ??
Jessica