OCS is written to support multiple payment service providers via plugins -- PayPal and manual payment processing plugins are included by default, and adding support for a new provider will mean writing a new plugin. This can be tricky for a newcomer to PHP, so I'd suggest doing some research to find out who in Barbados has a similar system to Paypal. There are two generak sorts of providers -- the banks and traditional institutions on one hand, who don't provide any services beyond the raw transaction processing, and on the other hand, there are businesses like Paypal who provide a lot more flexibility and ease of use for developers and web designers. If you can find someone like Paypal that does operate in Barbados, it will be much easier to implement than e.g. a bank's system, both because the Paypal plugin will serve as a close example, and because payment processing is less complicated that way.
Public Knowledge Project Team