By default, the web address of your application is under a 3GRC subdomain, for example if your company is called "mycompany" the application URL may appear as mycompany.3grc.co.uk.
You can map the application to your own domain, for example you may own the domain mycompany.com you can choose to map the application to www.mycompany.com or a subdomain such as app.mycompany.com.
To use custom domains you will need access to the domain's DNS service. You will be asked to add a validation TXT record, used to validate ownership of the domain, and a CNAME record to point your domain to the application.
Once the custom domain has been setup your application will be accessible on your chosen domain. All existing traffic will be redirected to your new domain so you won't lose traffic and existing links will still work.
To get started please send a support request to firstname.lastname@example.org and include the domain name and confirm you have access to modify the DNS on the domain.