If you don't know about unity then find out.
This is unity
<img src="http://i.imgur.com/LIRf7Dj.png" border="0" />
When you have it go to gameobject, then go to create other and click particle system.
Now you can fiddle around with the settings of the effect and then you record the fx with some kind of gif recorder.
<img src="http://i.imgur.com/VHTOksd.png" border="0" />
when done import it into construct 2 and done you are.
<img src="http://i.imgur.com/I6jkvmr.gif" border="0" />
If any part is not explained properly then tell me.