So that’s Network Solutions.
You should be able to setup the required TXT record manually in order to issue a Let’s Encrypt certificate (using ZeroSSL or gethttpsforfree or
certbot -a manual --preferred-challenges dns), however I am not sure whether NS supports any kind of API so that issuance and renewal can be done automatically.
At least, I cannot find any Let’s Encrypt clients that advertise support for the DNS challenge via Network Solutions.
You always have the option to move to one of the may free or paid DNS hosts that are supported by Let’s Encrypt clients (such as acme.sh) if automation is important to you.