Were do I put this File.

[sonic]

I found something its gates etc... its a .bgl but the readme did not say were to put it. ( its gates for an airport.) The whole name is .mod.bgl.

[MattNW]

Usually .bgl files go into a scenery folder. If it doesn't specifically say what folder to put it in I'd try this path first:

C:\Program Files\Microsoft Games\Flight Simulator 9\Addon Scenery\scenery

Just make sure you remember where you put it in case that isn't the right location and the sim crashes when you start your flight. What airport is it supposed to be for? If it's an add on airport you may be able to put the file into the "scenery" folder for that specific add on.