How do I save the game?
Solution 1:
It can't be done. You can trigger an autosave by finishing a level or buying an item, though.
Solution 2:
Don't worry about it - many games that use an autosave feature give a warning like this, even if it's just saved the game. You can read it as 'make sure you hit a checkpoint before you quit, otherwise you'll lose everything you've done since the last one'.
As long as you quit after hitting a checkpoint your progress will be saved.
Solution 3:
Playing on iOS I've found a way to trigger a save in the cantina without having to purchase an item. View one of the minifigs in the cylindric water chamber, change at least one of their parts using the white arrows and exit the edit mode. This brings up the Death Star briefly in the upper right corner indicating a save is happening.
Solution 4:
Go to the bar in the start of a new game and you can create a new autosave under the character option. You can visit bars within the game to save at anytime...