In OneOfficeERP, the Currency list stores the currency value, it's symbol and fraction unit. Most of the commonly used currencies are already present in OneOfficeERP. The exchange rates are fetched automatically according to the current market rate. You can also configure the system to use older fixed exchange rates by creating them in the Currency Exchange form.
To access the Currency list, go to:
Home > Accounting > Multi Currency > Currency
For example, this is how the Currency page for Euro: