Minecraft-creative-multiplayer. My own place to build?

Ok, so I play Minecraft like thousands of us but I encountered a question which the internet doesn't know how to answer… Weird i know. Well, anyway, I was connected to Jujucraft and went to the Creative server that they have. But when i wanted to build, it said I can't build there. So i jumped down, and found chumks of the world that players could build on. But I couldn't find a free one. I guess the question is: How can find a place to build? Maybe there's some command you type and it takes you to your chunk but I dunno. Any help?

On servers like that you have plots that are claimed so what you have to do is go and find one that isint claimed and claim it