The game will auto load and/or save all save objects on the game opening or closing if the relevant settings are enabled. To save the game manually you just need to call the load or save methods from the Save Manager class like so:

// Saves all save objects to the game save file.
SaveManager.Save();

// Loads all the save objects to the latest values in the save file.
SaveManager.Load();

It’s advised to not call these methods too frequently as they can cause a performance hit. It’s best to only call to save when you really need to like when changing levels or area’s etc.