when you buy web hosting it is expected for you to have a certain amount of competence about the service and how it works instead of knowing nothing at all. DH is not the type of host that wants to hold your hand (and rightly so). you cannot really expect them to help you with a service they do not provide. they give you the web server resources and it is up to you what to do with it (within company policy).
since you say you have registered a domain name it is simple to go to the panel and add your domain to be fully hosted. if you did not buy your domain name from DH you need to go to your registrar and make sure the domain is actually pointing to DH name servers. after that it is up to you to install wordpress though DH does have a one-click install (you would need to pick the custom install). you should have at least done some research about web hosts and how to use such services because this sort of thing is your responsibility to know beforehand.
it is not difficult to receive help if it is a DH service type issue but they do not give you support for 3rd party software. they do give you some convenient options on installing a few of the popular open source applications for you so you don't have to do it manually but that's really as far as it goes.