How to add Sub user with their URL

Hi
i have recently updated PlaySMS to 1.3.1 and in your feature list it was mentioned that it is possible to create sub reseller with their own URL branding. But i did not found anything on the forum on this topic. Can you please help me to get a guide on adding sub user / reseller with their own URL branding

Regards
ishtiaque

Login as user and go to Settings → Manage site

anton