I understand that you are using WCF to build the client, that connects to a remote web service, over HTTPS.
To do this, just modify the client-side config file for the WCF-powered app, replacing http://server.address with https://server.address, in configuration/system.serviceModel/client/endpoint/@address . like so:
<configuration>
<system.serviceModel>
...
<client>
<!-- change only the address string -->
<endpoint address="https://server.name/Whatever"
everything.else.stays.the.same />
</client>
</system.serviceModel>
</configuration>
(The path to the config file varies according to the regular .NET rules: whether it is an ASPNET app, or a service, or etc.)
OR you can set the address explicitly in code:
// instantiate new proxy to web service
var svc= new ServiceClient();
var e = svc.Endpoint;
e.Address = new System.ServiceModel.EndpointAddress("https://server.address/JavaServiceUri");
I strongly advise you to make the address configurable, and not hard-code it. That does not mean it must be stored in app.config, but it should be changeable. The proxy, too.