After creating a web application, you should next create a site collection:
1) Go to Central Administration -> Application Management and under Site Collection select "Create Site Collections".
2) Give it a title, url and then select the template you'd like to use.
3) Assign the Site Collection Administrators and press okay.
Now your site collection will be created. BUT, since we want to use the host headers, you should go to your C:\windows\system32\drivers\etc\hosts file and add the IP of your machine to that file along with your host header.