[Koha] Opac

Hello We have a domain: Bijrd.gob.do Also we have a subdomain where we have Koha and opac (in the neat future we are testing), With Koha we have not problems, but with Opac yes because when we want to starts it with have to type the subdomain name and the port number. Without the port number does not works We do not know how to solve this problemas and we can not published it with the port number. The port number is 8080. We could be change this? Thanks