Ok - you need to back up a bit and  understand how dnn works.

DNN is an application that runs in a single web site - you have obviously achieved this step.
This dnn application is able to be accessed by multiple aliases or domain names

By default when you install your first PORTAL - that portal can be set to be accessed by any number of aliases or domain names.
You do this in three steps.

Say for example you have setup your first portal on localhost and you now want it to be access as myportal.local or www.myportal.com

1. Register your domain with a DNS server / Domain registrar / Hosts file (if only being access locally for development)
if its www.myportal.com you would register with a domain registrar and DNS server
if its myportal.local you would add this to your Hosts file for local machine only access or add to your local DNS for internal access by any machines in your local environment

2. In IIS you add the domain to the bindings for the web site that dnn in hosted under.
Open your DNN web site - and add a new Binding for that domain name or alias
http myportal.local   80  * 
http www.myportal.com   80  * 

3. You then access your initial portal using localhost  or whatever you first set it up as 
Go to Admin ->  Site settings -> Portal Alias and add a new alias
myportal.local 
www.myportal.com

You can now access this FIRST portal using any one of three methods
http://localhost/
http://myportal.local/
http://www.myportal.com/

Each of these methods will give you access to the EXACT same content - which is being internally stored in the database for your portal as portalid=0.

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Ok - now we come to adding a SECOND portal - that being a portal that has DIFFERENT content to the first portal - but still hosted in the same web site by IIS.

You DO NOT need to create any separate virtual directories in IIS as the second portal will be running in the same web site under IIS as the first portal.

There are two options in DNN for this.
A Parent portal -  which is defined as a portal that has a DIFFERENT DOMAIN name from all other portals in the the same web site hosting 
http://www.mysecondportal.com/   or http://mysecondportal.local/  

A Child portal - which is defined as a portal that has the SAME DOMAIN name as other portals but is in a sub directory
localhost/secondportal/
myportal.local/secondportal/
www.myportal.com/secondportal/

Creating a child portal does not require changes to any area but dnn - you run the new portal wizard fill out the details and DNN creates your new portal - which has its own set of content - accessed via 

http://localhost/secondportal/
http://myportal.local/secondportal/
http://www.myportal.com/secondportal/

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Creating a parent portal DOES require some changes in other areas much the same as creating your first portal - registration of a domain name, and setting of bindings inside IIS -  

This is how the steps should go to add a SECOND parent portal to the same DNN web site hosting - a parent portal being a portal with a unique domain name and different content to the FIRST portal.

=======================

1. Register your second domain with a DNS server / Domain registrar / Hosts file (if only being access locally for development)
if its www.mysecondportal.com you would register with a domain registrar and DNS server
if its mysecondportal.local you would add this to your Hosts file for local machine only access or add to your local DNS for internal access by any machines in your local environment

2. In IIS you add the domain to the bindings for the original web site that dnn in hosted under.

Open IIS and locate the original DNN web site - and add a new Binding for the NEW  domain name or alias
http mysecondportal.local   80  * 
http www.mysecondportal.com   80  * 

ALL ALIASES are setup in IIS in the one web site - if you are going down the multiple portals per hosting system

3. You then access your initial portal using localhost  or whatever you first set it up as 

In Host -> Portals

You add a new Parent Portal - this time using the new alias:

mysecondportal.local 
www.mysecondportal.com

DNN creates a NEW portal - portalid=1  and interally maps all calls to the new domain to this NEW parent portal.

====================
You can now access this FIRST portal  -  portalid = 0 using:
http://localhost/
http://myportal.local/
http://www.myportal.com/

You can now access the SECOND portal - portalid = 1 using
http://mysecondportal.local 
http://www.mysecondportal.com

Westa

Right click website in iis 
Properties
WebSite Tab

In the website identification area
click Advanced

Add NEW

HostHeader is domain name 
80 is port
IP can be 127.0.0.1  or just Undefined.

Westa