Feeding garden birds from an upstairs window

 Hi everyone I’m new to this forum, this year I have decided to get a window bird feeder for my bedroom window. I used to face the main road and I didn’t have any joy with any birds coming to my feeder. In late October I moved rooms facing the back Garden. I don’t have any bushes, trees or flowers in my garden and I’m not able to get any either unfortunately. 

I admire the wildlife and I think it would be really cool if birds came to my feeder how can I attract birds to come to my feeding station that’s on my window? I live in Greenwich I’ve seen some birds fly around which is what prompted me in the beginning to get food for them. 

thank you