Resolved How do I apply my dns setting of domain? (Solved)

[Brownsugar]

I have plesk installed on Linode server,
and I added several domains in my Plesk,
I changed some DNS settings of one domain,
for example, I have a domain abc.com, server ip is 11.11.11.11,
I want sub.abc.com point to 100.0.0.0, I set A record in that domain's dns setting.
how do I apply changes to that domain?
Which NS should I use on that domain?

Additional question, I have bought SSL before, I use it on abc.com,
but my webmail also need a SSL, how can I only generate a SSL for webmail.abc.com?

Thanks.