You will need to obtain your domain name registrar such as fasthosts
That done, you will need to point the nameservers to the service you are using for your DNS resolving.
DIGITAL OCEAN
Digital Ocean: ns1.digitalocean.com ns2.digitalocean.com ns3.digitalocean.com
Once you have changed the nameservers for your domain to digital ocean with your domain name registrar you have to add your domain to digital ocean you can do that by following this
EXOSCALE
Exoscale: ns1.exoscale.ch ns1.exoscale.com ns1.exoscale.io ns1.exoscale.net (be sure to include all of these)
Once you have changed the nameservers for your domain to exoscale with your domain name registrar you have to add your domain to exoscale you can do that by following this
LINODE
Linode: NS1.LINODE.COM NS2.LINODE.COM NS3.LINODE.COM NS4.LINODE.COM NS5.LINODE.COM
Once you have changed the nameservers for your domain to linode with your domain name registrar you have to add your domain to linode you can do that by following this
VULTR
Vultr: ns1.vultr.com ns2.vultr.com
Once you have changed the nameservers for your domain to vultr with your domain name registrar you have to add your domain to vultr you can do that by following this
CLOUDFLARE
You will have some extra steps for Cloudflare which you can read about here: