How to connect a domain to Ubuntu (host: Microsoft Azure)?

Question

ubuntu

Rented a server with Ubuntu 12 Tls on Microsoft Azure. The domain name, say, by default is: syzran01.z0hndprmnicezg0xhm45syyhgd.fx.internal.cloudapp.net Zone DNS label: test-001.northeurope.cloudapp.azure.com IP address: 52.169.228.123. I purchased the test-001.tk domain. How can I direct (connect) this domain to the server? On Ubuntu, Sendmail is installed, when sending a test letter, we have the following domain: syzran01.z0hndprmnicezg0xhm45syyhgd.fx.internal.cloudapp.net .
Set up host and hostname files in /etc
Host:

127.0.0.1 localhost
52.169.228.123 test-001 test-001.tk

Hostname:
test-001
The domain itself is set up like this:
How can I set up a domain in a virtual machine so that when sending a letter (and in general) there is a test-001.tk domain