Currencies are need to define the Accounting currency of your company. There are some default types of currencies. To set the Accounting currency, click on appropriate button in Accounting currency column.
To change one of the currencies open its document, and change any of its fields as you need. Then click Save
To create new Currency go to Registries → Currencies, click on the Create button , and fill all the required fields, that are marked with red stars. Then click Create button . New currency will be created.