This article will teach you how to set up your site so it can be accessed from a non-salvationarmy.org domain.
Instructions
Go to your DNS settings at your domain provider (GoDaddy, etc)
Add a new CNAME record for wm4.salvationarmy.org
Go to the management portal (https://webmanager.salvationarmy.org/management)
Click Domain / Site Mappings
Select Create Domain, enter your custom domain, & click Save
Double click your newly added domain and click Add Site Mapping to map your site to this domain