Currency conversion - where is this stored in OTM? How do I update it?

We are starting to implement our Canada plant all our other facilities are in the US.   We have entered the the new rates in Canadian Dollars.  I see that when I do a rate inquiry, OTM displays the US Dollars (USD) and Canadian Dollars (CAN).  Where is this conversion factor stored maintained?  

How do people normally maintain this?  Is there an integration message that I can send in to maintain it?

Thanks,

Janice