Dynamic DNS wihtin dns-stock.com is free of charge.
Dynamic DNS points a hostname to a dynamic IP. This allows you to join your home network from the internet even if your public IP is assigned dynamically.
To setup dynamic DNS:
First, connect to your DNS-Stock account and add a dynamic DNS record to the DNS zone of your domain with the hostname you want (DNS section -> list Dynamic DNS records) ,
ex.: for athome.dns-stock.com you add an A record pointing to 18.104.22.168 with the hostname athome.
You will be asked to define a login and a password: This allows you to create new separate credentials only for the dynamic DNS updates.
Now enter the config menu of your router and configure as follow:
Dynamic DNS provider : User-defined
Update-URL : http://dyndns.dns-stock.com/?hostname=<domain>&username=<username>&password=<pass>&myip=<ipaddr>
Domainname: yourhost.yourdomain.tld (ex.athome.dns-stock.com)
Username: the username you defined when you created the dynamic DNS entry
Password: the password you defined when you created the dynamic DNS entry
The values passed to the different query string variables in the update-url (<domain>, <username>, <pass>, <ipaddr>) come from your router.
Please read the manual of your router.