How do I create a new world?

When I use the command featured in the video (look at bottom), I get a message saying, "you do not have any of the required permission(s): -multiverse.core.create" which leads to nowhere. How do I fix this problem and get permissions?

I have op on my server, but it still says I don't have permissions and redirects me to a nonexistent website "multiverse.core.create" Should I try a different plugin? I'll try that.

Oh, okay. And no, it says "unknown command at position 1: /<--[HERE]"

I looked on my Aternos server page and even entered my name into op again so I don't know why it doesn't work.

Great! Now I have op but I can't create the new world because "a Folder/World already exists with this name" and "multiverse does not know how to take you" to the new world. Also, is there a reason my skin remains as an Alex even though everywhere else it is my usual wolf skin?

I just realized that I can create other worlds with other names, but the problem is that now the server freezes and then crashes when it tries to create the world. It also claims that, like the first world, "the world could not be loaded because it contains errors and is probably corrupt." What should I do about that?

1. How do I reduce resource usage?

2. It doesn't matter what I name the world because it always has that problem. The first one was just like the video's (new_world).

3. Why does my server always deop me every time I rejoin? How do I fix that?