Btw, please never use GoDaddy. They are the worst. I should probably write a separate piece on why GoDaddy is absolute garbage.
Alright, so you've chosen your domain name already? Now you just have to register it. Easy enough. Go to Namecheap and check your domain's availability.
I've decided to go with woodwaker.com for my new niche site and, just as expireddomains.net was claiming, it's available. I'm going to add it to my cart and pay for it. I've had an account with Namecheap for 10+ years. You'll probably need to create one and add your personal details before buying. Put your real personal data in, as only this way you will legally own this domain name.
Be sure to click "auto-renew" and enable your free Whois guard.
Once the domain is purchased, you can click "Manage" to proceed with configuring the nameservers.
You need to change the first option to "Custom DNS." I'm using Cloudflare, so I'm putting the nameservers appointed to my account here. Check the Cloudflare setup tutorial for more information.
That's it! You bought your own domain name and it's fully configured at the registrar.