Remmina troubles

Installed remmina and now trying to run it with sudo remmina. But getting this:

[code]No protocol specified

** (remmina:9005): WARNING **: Could not open X display
No protocol specified
Unable to init server: Could not connect: Connection refused

(remmina:9005): Gtk-WARNING **: cannot open display: :0[/code]

Any ideas?

This chapter:
Safely Use Root Commands