I have never been able to get a forex chart using IB. It always says no historical data available at the top of my screen. I trade futures however, and you can get charts for those. To tell the truth I only use IBs charts for the time and sales data. I route the data to my own charting program - much easier and comfortable to work with.
I believe you can use Sierra charts,you can read about them here hope this helps. http://www.stockstoshop.com/sierra.htm