How should i buy domain name ?
It’s super easy. Just pick a registrar and buy your domain (if it’s available).
For example, if I were to buy anaskhan.net, I could get it from Dynadot for $5.99.
Trustworthy registrars are Bluehost, Namecheap, GoDaddy, and I can vouch for Dynadot.
I can vouch for Bluehost and Hover.
Incidentally, you can get a domain free for a year (terms and restrictions apply) with Namecheap by completing the Make a Website course.