Importing a pre-existing save
First login to your server's control panel and stop the server
Locate the save's .zip file on your PC that you wish to upload.
Use an FTP Client to upload the save's .zip file to the 'saves' folder on the server.
https://hosthavoc.com/billing/knowledgebase/582/How-to-use-an-FTP-client-with-your-Factorio-server.html
Rename the save's .zip file to be default.zip , if there is already a default.zip in the saves folder, delete or rename it first.