I'm sorry but, it won't serve either you or me if I just tell you how to do make your game. To be honest, in most cases I would not have even responded to your question because it shows that you have not done anything to learn the program before asking someone else to do the research work for you. On the other hand, if your post had looked like you really put the effort into trying to understand and still were stuck on a specific issue, I (and other advanced users like me) would be more than happy to go out of our way to help you understand. The only reason I felt it necessary to respond in the first place was because you re-posted the same question so soon after the first post. This is just bad forum etiquette and I felt it would be best if someone let you know.
What you need is an understanding of how the features in Construct work. And, you'll rarely find a tutorial on your specific requirement. You should however, be able to find tutorials about the features of Construct to help you better understand and make use of them. The 2 features I told you to look into will give you everything you need to accomplish your project. The COMPARE TIME event will define when to spawn the "shuriken" and the BULLET behavior will make it move from left to right. Those are the types of tutorials you need to look into.
To give you a starting point, look at the following links:
https://www.scirra.com/manual/124/system-conditions (look under the section for "Time" to understand what "Compare Time" is doing)
(This is a YouTube tutorial I looked up that shows how to spawn a bullet and use the BULLET behavior so it moves across the screen)
Now if you go through the info on those links and there is still a question about how something works, feel free to ask me. Be specific about what it is that does not make sense and I will be happy to help, but, you need to put in some effort first.
There is a wealth of training information already online. Make use of it. If you don't take the time to learn the tool, you will spend far more time coming to the forums to ask these types of questions. Before trying to complete your game project, go through the beginner tutorials. Then, if you are still having trouble with a particular subject, use the forums to ask clear, focused and specific questions.
Good luck with your project.
[Edit] I was just reading back through your post and realized, you could even use the EVERY X SECONDS event instead of the COMPARE TIME event.