When I Add A World ToMy Server How Do I Go On It?

Koz4Christ is correct regarding multiverse commands However, those commands are not in standard bukkit and require the use of the multiverse plugin.

You can get that from here:

http://forums.bukkit.org/threads/edit-misc-tp-fun-multiverse-2-3-world-management-bukkitdev.3707/

Then you will want to download and install it on your server. Which I assume you know how to do.

Then just use the command /mv import <world name> <world type>
where world name is the name of the folder of the world and the world type is either normal nether or end.

To go to that world use /mv tp <player> <world>
where player is the player you are teleporting and world is the world you are going to

Dont forget if you use a permissions system to add in your permissions and such for the plugin

If you want more references on installing and using this plugin go here:

https://github.com/Multiverse/Multiverse-Core/wiki

You can also install multiverse portals and create portals between worlds. If you want that feature make sure you install that added plugin, also on the main download page linked at the top.

Good luck. Let me know if you still need help.
BoomTownMC

I believe you'll need to use some multiverse commands to import the worlds.

/mv import <worldname> normal

Simple get the world name and change it in your Server.properties file