So practice as Luigi or Ice Climbers if you don't already, they are the easiest to see the effects of wave dashing on. Heres what you need to do. Jump really high, then air doge down and to the right, then jump really high and air dodge down and to the left. Do this a couple of times until you can do it over and over consistently as easy and pointless as that sounds. Now do a little jump (short hop) and air dodge down and to the right/left, do this until you are comfortable with it. Now is the tricky part, start air dodging earlier and earlier after your jump, until you get to a point where you are airdodging and jumping almost simultaneously. When you get to that point, you are wave dashing. Its a matter of slamming into the ground while you are doing an air dodge. Thats the easiest way to think about it. And its also practice. Even after you think you have it down you will still mess up occasionally.
Also it is important to understand applications of wave dashing. Look online for guides on WD OoS or wave landing on stage. The applications are more important than knowing how to wavedash itself. Hope this helps!
