domain Subdomains

I am starting to do some advertising for my web clients and myself. I would like to set up subdomains for the ads and I cannot figure out how to point a subdomain to an internal landing page. 

For example, I'd like to point specials.example.com to www.example.com/specials 

But I can only figure out how to point the subdomain to my homepage, which isn't helpful. I am using GoDaddy and Google domains for hosting the domains. 

Any help is appreciated. 

1. Log into Go Daddy cPanel.
2. In the Domains section, click the Subdomains icon.
3. Under Modify a Subdomain, click the Manage Redirection link to the right of the subdomain you wish to redirect.
4. In the text box, type the URL to which you would like visitors to be redirected if they go to the subdomain (e.g. http://domain.com/optional-stuff).
5. Click Save.