I assume from your not-clear question that you have created a new site, and that you would like your domain name to use the new site. It is not clear if you changed hosts, or installed the new site in a new folder on your existing hosting place.
If you changed hosts, then you will need to change the nameservers for your domain to point to the new host. This is done wherever your domain is registered. Your new host will have instructions on the proper nameserver value to enter at the domain registrar.
If you installed/created the new site on your existing host, in a separate folder, then you will need to point your domain to the new folder. Your hosting place should have instructions on how to do that.
If you installed/created the new site in the same folder as your existing WP site, then that is a bit harder. Your new site files are mixed up with the old WP files, and (probably) your htaccess file is still pointing to the old WP installation.
You could change the htaccess file to whatever the new site needs, but I would (if possible) re-create the new site in a new folder on your hosting place, then use your hosts’ instructions on how to point the domain name to the new folder.
And if any of this is not clear, then you need to provide more details on how you created the new site, the folder structure, whether you are using a new hosting place or the same hosting place.