In each .htaccess file, there is a line that says:
RewriteBase /
Read the comments above this line, and edit as needed.
The best way to find out if you have configured your htaccess file correctly, is to test your site and make sure it functions properly
If you installed x-cart into your site root (/), then you shouldn't need to edit anything. If you installed into a subfolder (/shop), then rewritebase needs to be edited
EDIT: Again, if your site is working fine, you
don't need to mess with the .htaccess file