Newby question: where do I find the save game function?

How can I save the game? Is there a keyboard shortcut or an icon somewhere?
When I load a saved game, the save game list shows the autosave and lots of blank entries in the list, but I haven’t found out how to save the game under a custom name.

In the game screen click the ‘end this game’ button at the bottom right, it will take you to the menu, there will be a new menu button ‘save your progress’. Click on autosave and rename.