I don't know where to post this but my question is, Can you register your server even if it's soon to be opened? But the server is already up and you can register already. It's just that it needs promotion first.
Refer to this link: http://forum.ratemyserver.net/server-advertisement/server-advertisement-rules/ (http://forum.ratemyserver.net/server-advertisement/server-advertisement-rules/)
If your server is currently up and running as well accepting players registration, you may register on our website and/or have a post in this forum's advertisement sections.
In both cases you must follow the rules presented to you. At the very least, your website must have your server rates / feature list, have a downloadable client and a way of contact such as a forum / discord / facebook page to support players outside of the game.
For the 'soon to be open' case, we recommend you only post / create a listing within 7 days of opening. Because reviewer must have played on your server to write a review, if we see you are getting review but your server is not yet playable then those reviews will get removed.