You can set up your own domain by making sure that the DNS for your domain points to 62.129.136.33 for both the www.yourdomain.com and yourdomain.com entries.
Make sure that you do this *BEFORE* you try to create your own domain setup or the installation procedure will fail. (it needs the domain to be up and running for the configuration).
Changing domain name after
Is it possible to change the domain name after the new website is created? For example, while developing the website I use a subdomain, but later on, when advertising it for public, it might be useful to change to a upper level domain.
YES
Yes this is possible, please notify me if you want to change your subdomain into a upper level domain.