If I know which line isn't cool in the program code, how can I find it and edit it?

I keep getting this fatal error, and it keeps citing the same reason.

E : \Drive1\temp\buildwar3x\engine\source\Jass2\instance.cpp

Line: 263

Can anyone elaborate on what problem this is and how I would go about editing it?

That's a c++ source file. This forum is about Jass.
If the world editor tells you something is wrong with a line in your Jass script, it is often because the previous command is invalid.

Well thank you very much, I probably should've guessed that when part of the extension is buildwar3x. In any case, could a mod move this to the appropriate forum? Thanks.