worry no more, you'll learn how to do that right here.
Here's How to change Facebook Ad currency from Default to your preferred currency
Simply click on Payments >> Payment Settings and you will see options, please refer to the above picture for help or follow this direct link Facebook Ad Manager Select your new currency and you're good to go.
Also Note that:
Once you choose a new currency, you’ll automatically create a new ad account and if you already have old account it will be closed and all ads created with your old account will stop running. Your billing of previous ads with old currency will also be billed from old currency.