You should put this in a script in ~/bin and call it from startup applications.
First make the ~/bin folder if you don't already have one:
Every time you boot, this folder will be automatically added to your paths
Next, create the new file and start the edit:
and past the contents into it:
xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
xrandr --addmode VGA1 1280x1024_60.00
xrandr --output VGA1 --mode 1280x1024_60.00
Then save and exit gedit.
Now you will need to change the file so it is an executable script:
chmode +x ~/bin/setscreen
You can now call the program at any time by opening a terminal or console and typing:
You should now open up startup applications and add the file /home/username/setscreen and make sure it is selected for start.
Really though, what you should be doing is adding this mode to the /etc/X11/xorg.conf file so that it is working correctly right from the login screen. This is a different and more complex problem however, and you should probably ask a separate question on how to do this.