Edit DayZMenu.ini in your loader folder.
The default is
[Scripts]
Default=scripts\menu.sqf
Key=45
I think.
Let's say the menu loader file is called mah.sqf and it's in the folder called scr in the oa directory.
You will need to edit the Default= line to match the mah.sqf file.
In this case it would be Default=scr\mah.sqf
The sqf file you're looking for is usually called
mah.sqf
menu.sqf
startmenu.sqf
ajmenu.sqf
or something similiar.
I know my explanation sucks.
If you still can't get it to work,add me on skype.