How to import with xampp?

In the URL field, you have to put the URL of the home page of your Joomla site (for instance https://localhost/joomla)
And you have to put ?localhost? as the Joomla database host.

i did that, but I wonder is it possible to import comments somehow? I have ijoomlacomments on my site, I guess I can change to another extension

No, the comments are not supported. They are not a part of Joomla. They are an extension with a Joomla plugin.

The comments are now migrated with the Premium version and with the JComments module. You can purchase this version and the JComments module on https://www.fredericgilles.net/fg-joomla-to-wordpress/