Can I put crackle paint on a cheap wardrobe I bought from WalMart?

You can, but you have to know the construction of the wardrobe to do it. If it is pressed wood or MDF with no veneer, the process is a little easier. If it is melamine over MDF (more common) you have to first rough up the surface, then use a stain blocking primer so that your base coat adheres well and you can use the crackle medium and top coat without worrying about flaking, peeling and bubbling.