retired US Citizen married to Canadian both living in Canada with US retirement income.

I'm a retired US citizen living in Canada.  I'm married to a Canadian green card holder.  I'm recieving SS and my wife is recieving both SS and US retirement income.  I know we need to file in both the US and Canada, but am confused where to file first and which contry to report what income to.  We also have a small farm in Canada and own Canadian real estate.