I think you got the part about creating te site. How you access it depends on whether you are using host name based sites or folder based sites.
If using folder sites your first site must be a root level site like http://somedomain.com/ or http://localhost/
Then after you create a new site you specify a folder name so if you make it folder1 for example, then you would access the new site at http://somedomainc.om/folder1/Default.aspx or http://localhost/folder1/Default.aspx
For host name based sites you must have a fixed ip address and you map all the host names you want to use to that ip address. After creating the site you see the host names tab in site settings, add the host name there.If using localhost on your local machine you can enter host names in the hosts file on your machine as specified at the bottom of this page.
Hope it helps,