you can set up a multisite system or you can create a new wordpress installation (subdirectory/subdomain/domain). Creating a completely new installation is less complex and sometimes better because many plugins, etc don’t support multisite. However if you want to use multisite you can refer to this tutorial: http://www.ostraining.com/blog/wordpress/wordpress-multisites-tutorial/
You need a license per domain – so i.e. if you’ve two domains you need two licenses.