You will need to be logged in to your iwantmyname account.
For Cargo 1, you can start the install here:
To finish up, you'll also need to login to your Cargo account and add your domain name there under Settings > Use a personal domain name. Some additional useful information may be found here: Configure a Personal Domain.
For Cargo 2, you can start the install here:
That will set up the Cargo 2 DNS records. We recommend that setup if you are using additional services, like email hosting.
If you prefer, you can use Cargo's nameservers instead. To set that up, click on update nameservers in your domain's dashboard, then select the Cargo nameservers from the drop-down list, and save the new settings.
Once that is done you will need to complete the setup in your Cargo account. Their instructions are here: Using a Third-Party Domain.
You may see things start working within a few minutes, but please remember that it can take up to 48 hours for DNS changes to fully propagate around the internet. So your website may not show up in all browsers immediately.