Most hosts provide you with a temporary URL where you can access your site while you're setting it up, before you go live. Ask them what that URL is or look in your hosting control panel.
When you're ready to go live, you're going to need to switch the DNS to point the domain to your new server. Your host will have provided DNS servers when you signed up - for example, they look something like:
ns1.myhost.com
ns2.myhost.com
(examples only)
You will need to log into your domain registration control panel (wherever you registered the domain) and go to the section where you update your name servers (aka DNS) and put in the information provided by your host.