Particles over player

I've been using the tutorials and so far it isn't helping me, so I figured I'd ask for help outright.

I'm trying to figure out how to call a particle effect, using code. For instance, the player hits "b" and there's a sound effect and a particle effect appears over the player. I have figured out the keybinding, sound, and how to get the position of the player to place the effect but I can't seem to get the effect to appear...

A sample code piece would be appreciated but understanding how it works is even more appreciated...I'll continue trying this tonight...hopefully I'll find an answer soon.