Upload and Use a Custom World on Your Minecraft Server.

1. Log in to your server's Pterodactyl panel. Select the server you would like to use a custom world with. 

2. Stop your server if it is currently running. This prevents the server from creating any new files or modifying existing ones.

3. We recommend you also create a backup of your current server files to prevent any files from being permanently deleted.

4. Once you've stopped your server, open up FileZilla or any FTP client of your choice and access your server directory.

5. Upload your custom world using FileZilla.

6. Once your custom world has been uploaded, return to your Pterodactyl panel. Locate the Level Name option in the server.properties file and enter the name of your custom world's folder on the textbox next to it. 

7. Click on the Save button found at the top of the page.

8. Start your server so that your custom world can be loaded into your server.

That's it, you can now use any custom world in your Minecraft server!