Do you mean to start at boot or at login. These are two different things, even if you use autologin.
When at boot it will most probably be run as root. This must be done, by either adding it to /etc/init.d/boot.local (which is executed ver early in the boot sequence, maybe to early for your application), or by providing a script based on /etc/init.d/sceleton.
When at login it will be run as the user that logs in. And it will be run again when that users logs in for a second time, etc. This must be done in a Gnome way, where I can not help you, but I have no doubt others can.