If you have decided to use the IIS option after the Pyramid installation, you can add the site manually. 

First, you need to install the following IIS modules :

To install "IIS URL Rewrite Module 2" and "Microsoft Application Request Routing 3.0" please download and install them using the links below:
Note, that before installing them, you'll need to close IIS first.

• Microsoft Application Request Routing 3.0: 
  https://www.iis.net/downloads/microsoft/application-request-routing
• IIS URL Rewrite Module 2: https://www.iis.net/downloads/microsoft/url-rewrite
  NOTE: The Application Request Routing should include the IIS URL Rewrite Module, but if it's not, here is the URL to install it.

Once the above two IIS add-on's have been downloaded, run the installer and follow the on-screen prompts.

Once the above two models have been installed, activate the proxy as shown below:
Open IIS >Double click on the server name(1)>Double Click on "Application Request Routing Cache"(2)
 
Click on "Server Proxy Settings..."(3)

Then Tick the box "Enable proxy"(4)>Click on Apply(5)

Secondly, create a new website and point it to the following location:

C:\program files\pyramid 2018\repository\iis

For the site name call it "pyramid2018", for the Physical path point it to C:\program files\pyramid 2018\repository\iis, for the hostname it can be anything but please note that you must add this to your DNS or local host file.

Then double click on the newly created site >URL Rewite. Double click on the first rule and make sure the Rewrite URL is: http://localhost:8181/{R:1}

Once the above steps have been done, please do an IISRESET and then try to access Pyramid 2018 again using the newly created IIS website.

NOTE: Ensure that the relevant ports are open on the firewall: 80 for HTTP and 443 for HTTPS.