You cant change the servers with existing characters.
The only way to do is by deleting and making new character.
You can change worlds by using the game's teleporter system. But if you are looking to play with friends, either wait for the update or start from scratch
"To improve the game experience, we have decided to increase the capacity limit of individual servers" "You can choose to play on other servers, and we will do our best to provide a stable and smooth game experience. "
forums.exputer.com
Also they have added the feature to make multiple characters ahead of official release. So make a new character slot to change your server. Altough you may have to start from scratch