help home made wood furnace

I made a wood furnace and installed it in my attached garage. The furnace burns nice. I fed the supply through the band board on my house and tried to tie into the return air. This worked but not very efficiently, it takes a huge fire to stay decent, and it eats the wood. Can anyone advise me on how to supply my registers. Or let me know if I am wasting my time trying to do this. Can I chang it to the supply in existing furnace or am I trying to move my air to far. Someone please help. thanks