[ubuntu] tried to swap unity for different desktop and now all i get is a command line

I wanted to get rid of that anoying sidebar so i went to a site called ubuntu geek which recomended that i put this line into the command line
sudo apt-get install gnome-session-fallback
i did that
and then i switched off the computer and then switched it back on and now i have no desktop at all just a command line
please help