Mapping your own domain onto a Deskish url is currently not possible. However, it's fairly easy to forward your own domain to your blog or a single desk. That way, typing in www.yourdomain.com into the browser will lead to www.deskish.com/username or www.deskish.com/username/deskID.
In order to forward a domain, please follow these steps (sequence and wording may be slightly different for every provider):
Go to your domain provider's website and log on to your account. Find the 'Domain' settings. Open the settings for www.yourdomain.com. Look for "redirect" or "forwarding" or "destination" and add your blog's (www.deskish.com/username) or target desk's url (www.deskish.com/username/deskID). Save the changes. Test the new settings by typing in your domain into your browser's address bar. Please note that changes to the domain settings sometimes don't take effect immediately.