I believe the process is the same for both Canada and the United States although there are 2 different organizations running the same type of program.
There is an application, you can fill out online or mail it in. On the application you draw an outline of your garden, details on types of plants/vegetation etc, water sources, and shelters as they relate to providing food, water and living space to wildlife to raise young. They also ask if you use pesticides,
They charge a fee and when your application is approved you recieve a window decal, yard sign and certificate for framing. I have my gallery - you have an ID# so you can share it - listed on the US site because the Canadian one does not have a gallery to showcase gardens yet.
The benefits of a certified garden are all for the critters, there is no other benefit than a huge feeling of personal achievment, but boy it does feel good, and I enjoy the fact that I can justify many more hours in the garden cause now it's for the wildlife!!
The US org is called the National Wildlife Federation and the other is the Canadian Wildlife Federation.
And let's be serious to a gardener, talking about a garden is second only to being in it!!