At first the game seems like a simple "don't make the wrong roll" kind of game. But ther is more to it than that. You need to carefully manage your discard dice as well as the pairs you can make. It seems a bit frustrating at first, as you can never seem to get a positive score. But with a little planning, you can do it.
Your first scoring pair will summon the skulls. Later pairs will clear them. Rows with skulls are worth -100 points. Once the skulls are cleared, you can start making positive numbers. Good luck!