if you are talking about the simple hyphen smash, it is just an upsmash from a dash...so do an upsmash while you are dashing.
If you are talking about Dash Attack Cancel, that is character specific, and sadly, Pikachu cannot perform it. But to do it, you have to dash, do a dash attack then quickly upsmash to cancel. This results in a boost for the upsmash, using the momentum of the dash attack.
Characters like Snake prosper with this.
If you are using a game cube controller, dash, press down on the cstick to initiate a dash attack, then press up and z simultaneously RIGHT AFTER the the dash attack.
