How to connect self-host Ubuntu server to a Domain I bought

I have successfully setup my Jitsi on a Ubuntu server in hostname. I can access it in local machine web browser by typing hostname but I don’t know how to connect that server to a DNS.
I’m not familiar to Web hosting or Linux. Can anyone help me to this step by step. I just want to fast setup to make it public to the internet.

First you need to buy a domain from a registerar and then to create a DNS record which points to your server’s IP address for FQDN