How to create own domain in each conference?

To do this, you will need to modify config.inc.php’s base_url settings for each conference, and enable RESTful URLs via mod_rewrite (or similar).

To configure RESTful URLs you will need to add code to your webserver configuration (for example, mod_rewrite in Apache). There is an old conversation on this on the previous forum:
https://pkp.sfu.ca/support/forum/viewtopic.php?f=2&t=2616

See also this parallel in OJS and IIS: