Hiya Anakin I done a post a couple of days ago regarding this and you have to actually go in person either to Manchester or London whichever is nearer to you.
Process is simple basically for your wife 1 passport photo, passport & copy, BRP & copy, marriage certificate & copy also flight itinerary showing actual flights booked and paid for and your passport & copy.
If you get an early appointment visa can be processed within 2 hours so really simple and a lot more accommodating than other embassies....
PS: Schengen application is filled in online and then printed off to secure an appointment at the embassy and at the time my wife done it it was a wait of around 3 weeks for next appointment date...