Step 3: Put into molds
You have several options here.
I melted several different kinds of chocolate so I could play around with decorations. I did some layered, some with dots of different colored chocolate, some with squiggles.
Or you can just do plain.
For adding dots and squiggles, you could of course use a pastry bag, but a quick and dirty way of doing it is to use a medicine dispenser syringe, just suck up your chocolate and dot it back out again. I found that White chocolate dots on regular chocolate worked pretty well, but dark chocolate embedded in white chocolate did not 'stick' as well. I suspect that it would work best if you used different colors of tinted white chocolate, so you wouldn't have the issue of different consistencies.
Just pipe your dots, etc into the mold, let set briefly, then pour/spoon over another color.
For layers, just pour or spoon in a small amount, let set, then spoon over a second layer, let set, then a third.
For a 'hidden' center, fill the bottom with color A, spoon a dollop of color B in the center, then completely cover with color A.