You've to install a browser first. Ben Novack was almost correct. But Libranet does not install Galleon, even if you've chosen to install Gnome, for example. You've to install Internet or Network packages. I doubt you can install opera through apt-get. Mainly because opera is not free. Do first:
apt-get update
apt-get install mozilla
That would install you mozilla 1.0 I think. From there it's easy to get Opera, if you really want that one indeed
.