Create a java-action that uses Exchange Web Services (EWS)
Create a settings entity. Make a connection like this
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
ExchangeCredentials credentials = new WebCredentials(settings.getUsername(), settings.getPassword(), settings.getDomain());
service.setCredentials(credentials);
service.setUrl(new URI(settings.getURL()));
Use this documentation as starting point for creating appointments