Unfortunately unlike other games Factorio won't generate a new world by simply changing the name of the save.

If it does not locate a .zip matching the name you specified in the settings on ClanForge the server will refuse to start.
To get a new world you would want to start up Factorio client side and you will be able to generate a map there with the options you choose for the save/map.

Once you have this generated you can attach it to a support ticket and submit it to our Support Team who will upload this into your server save directory.

We are currently working on a World Management tool which will allow you to upload it however this is still in development.