Swarm 2015.1: User Guide (May 2015)

Register a short domain name, or if you control your own DNS server, a short domain name for your network.

Point the short domain name at your Swarm host.

Edit the data/config.php file and add the following configuration block:

<?php
    // this block should be a peer of 'p4'
    'short_links' => array(
        'hostname'  => 'myho.st',
    ),

Replace myho.st with the short domain name you registered/configured.