Press Escape to open the in-game menu.

Click “Server Manager”

Enter a name for your Save & click “Create Save”.

(Optional) Choose the session you want to save to, enter a name for your save file, and click Save.
Press Escape to open the menu.

Click Server Manager, choose your server, and open Manage Saves.

Click Load Save, pick the session and specific save file you wish to load, and then click Load.
Your world will begin loading, and once finished, you’ll be able to jump right back into your saved progress.