Hello players!
To create your own world in Multyplayer, please follow these steps:
1. Click on Singleplayer button, choose creative, choose world from the drop down menu (random world, flat world, predefined world), enter the world name, click on OK button.
2. Build something on your new world! Click on Menu and click on Quit to Title.
3. Find your world in Singleplayer Mode.
Read more about How to upload worlds to Multiplayer by clicking Here.
Ok...