There are two possible variations on how to approach this, dependent on whether the site in development is hosted elsewhere or whether you're creating a WordPress site on 20i:
Developing your site at 20i but it is hosted elsewhere:
You may be using the temporary URL within StackCP whilst you develop your site. To take the site live you'll need to do either of the following:
1. You can either point the domain to our nameservers which are:
2. Point the domain to the A Record that is located within StackCP > Manage DNS.
If you are using the temporary URL within StackCP and you have a WordPress site, you may need to do either, or both of the following:
Update the temporary URL within WordPress Admin:
There is further information about this here: https://codex.wordpress.org/Changing_The_Site_URL