To setup a subdomain on the Uniform Server, your best option is to use a VirtualHost. Once your VirtualHost is set up, you need to also configure your domain, normally with a CNAME entry, pointed to the same location as the root domain. This basically tells the DNS to direct requests to the subdomain to the same location as requests to the main domain. Therefore, both requests end up going to your Uniform Server.
Example DNS Records:
Working With Localhost
Without direct access to the Records for localhost, if you are developing on a local server, see Working With The HOSTS File for more information on setting that up.