When I try to edit my lilo.conf file I cant do it because I don't have permission. I was in it before and now I can't get into it. How do I unlock or give myself permission?

I tried su from root and it said no server connection. Something about X host. This error message comes up when at root.

kdesu kwrite lilo.conf

Error: Check if you have read access to this file. This error comes up when I try it with an editor.