Even though only USD is enabled.
So in case we require using any other currency then the currency has to be enabled.
The define currency option also allows us to enable and disable a currency & define a currency that is not in the ISO Standards.
General Ledger Setup -> Setup ->-> Currencies -> Define
Save the form using either the Save icon or CTRL + S Key Combination
Precision is the number of decimals that are used for regular transaction while extended precision is the number of decimals to be used at the time of calculation
You can enable the currency for a fixed period by entering a start date that is future, and also you can end date a currency to disable the access with a predefined date.
Entering a start date will not enable a currency unless the enabled flag is enabled, but entering an end date with the enabled flag will disable the currency.