It is hard to snowboard on my new board?

I got a new snowboard for christmas and it is bigger than my old snowboard. I have been snowboarding for 3 years on my old board and i am really good, but when i tried my new snowboard which is about 1 1/2 feet bigger than my old one I could not control it very good. I fell a couple times and had a hard time turning left. (I snowboard with my left foot in front). Is there anything i need to do to fix this? Should my bindings be adjusted or further apart on the board? I just want to know why it is so hard to snowboard on my new board compared to my other one. I am 5" 6 if that helps at all