If you only purchase products using your local currency, no currency configuration is necessary.

If on the other hand, you purchase products from suppliers with different currencies, you will need to set up one or more foreign currencies, with exchange rates.  To do this, go to ApeksOPS > Settings > Currencies.

When you set up your Suppliers you can enter a Currency for each.  When you enter a Purchase Order, ApeksOPS uses the Currency of the Supplier and the Exchange Rate of that Currency.  You can alter the Exchange Rate for individual Purchase Orders when ordering or receiving stock.