Ubuntu Server is, by default and by design, a text-based system. Why would you want to use up 200MB of RAM on stuff that isn't serving web pages or running applications over the network? You wouldn't. It doesn't make sense.
However, if you installed this thinking you wanted to run servers from an Ubuntu Desktop machine, you can do that with the standard Ubuntu install (I run several servers from this desktop). It's all fairly modular.
Similarly you can install the standard desktop meta-package (
ubuntu-desktop) into a Server install. As this is a new install you'll also need to update the package lists. You'll need an active internet connection for this to work.
sudo apt-get update
sudo apt-get install ubuntu-desktop
If you don't have a wired connection and need to configure this for a wifi first... Well honestly, you'll be quicker just downloading the standard Desktop CD and reinstalling.