Joining the server
A licensed account, the address, the whitelist, and why renaming breaks nothing.
A licensed account
Sign in with your own licensed Minecraft: Java Edition account. A pass buys server access; it does not include Minecraft. Bedrock Edition cannot join.
The address
The Everdawn world's address is play.everdawn.net. The Vanilla world is not open yet: its page on the site shows its address once it opens.
Once the pack is installed — through the CurseForge app or Prism — there is nothing to type: Everdawn is already in your server list, put there by the Desired Servers mod inside the pack.
The whitelist is the list of accounts allowed to join. Knowing the address does not grant access.
The whitelist
Access follows the account's UUID (its permanent identifier), so changing your username does not remove access. Join with the account whose username you entered at checkout. The form checks that the account exists; it cannot detect a typo that happens to name another real account. If you entered the wrong username, contact support.
How long it takes
The server adds your account automatically after it processes the confirmed payment. If you were charged but still cannot join after a few minutes, do not pay again. Follow connection troubleshooting or contact support with your Minecraft username.