Configuration
To use the Currencies extension, you need to download it from the client panel (it is available to Pro and Pro+ license holders only), and install and activate it from the wp-admin -> Plugins -> Add New -> Upload panel like any other WP plugin.
Once activated, you can find the settings in the wp-admin -> Classifieds -> Options -> Currencies panel.
Currencies List

You should see a list of about ~170 currencies. If your currency is somehow not on the list, you can add it by clicking the “Add New Currency” button and filling out the form.
On the list, you can quickly filter the currencies list by entering the currency ISO code or name in the “Filter currencies …” input.
The list also gives an option to edit the currency rate either manually by clicking the “Edit” button or to sync all rates at once by clicking the “Sync currency rates” button, however, please note that automatic syncing requires integrating with the exchange rates API service.
Adding New or Editing Existing Currency
The form fields should be self-explanatory, one important thing to note is that in the Currency input, you should enter currency’s 3-letter ISO code. The complete list of currency ISO-4217 codes you can find here https://en.wikipedia.org/wiki/ISO_4217.
If you are editing the currency, you can restore the original values from the currencies list by hovering the mouse over currency row and clicking the “Restore to default” link.
General Settings
The settings for the Currencies extension you can find in the wp-admin -> Classifieds -> Options -> Currencies -> Settings panel. It has the following options:

Default Currency – The default currency is actually the one you set in the wp-admin -> Classifieds -> Options -> Core panel. The default currency is basically the one that will be selected by default in the Currency input field (if you will show the currency in this input).
Default Exchange Rate – This field is for future use, for now it is best to use USD or your default currency.
Default Price Field – Checking this checkbox will automatically replace the default Price input with the new currency field that allows changing currencies, entering price as range and etc. The default settings for this field you can configure in the Settings below
Hide Decimals – By default the plugin will format prices using the selected currency settings, so for example, for USD it could be $1,000.00, while this looks good in the input, in the list and details pages you might want to show the price without the cents like this $1,000. Note the cents are hidden only if the cents are 0.
Auto Conversion – When you check this checkbox the plugin will convert prices in the list and ad details pages to either user selected currency or the default currency, otherwise the currency selected when posting an Ad will be used.