WordPress has built in tools to export existing content which you can import into another WordPress site, but if you have a large site, you might run into this error when importing your exported data file:
Sorry, there has been an 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.
There’s two parameters here that you can increase: upload_max_filesize and post_max_size. If you increase these, post_max_size should be larger than upload_max_filesize (more info here).
Next up, if you have a very large site, no matter how much you increase these params, they still might not large enough to upload a single export file. In which case, there are utilities to split the exported data xml into multiple smaller files. Here’s one example here I just and it seemed to work well.