It would be fantastic if one could just melt chocolate wihtout much attention and mold it into whatever use came to mind, but that’s not the case. Chocolate that has been simply heated without regard to temperature can form a streaky mess with off flavors. The right way to reshape a solid mass of chocolae is with “tempering”: a controlled melting that eases the choclate into the narrow temperature window (around 90° F) where it is rendered malleable by the warmth, but not damaged by the heat.
I did this recently via the traditional stovetop method using a double boiler (a bowl set over a pot of steaming water), with close monitoring of the temperature using an instant read thermometer (I use a Thermoworks Thermapen).
I used the instructions from about.com, which essentially say to first heat up the chocolate to a relatively high temperature (110 °F for white or milk, 115 °F for dark), then cool to a working temperature (87 °F for white/milk, 90° F for dark). While it seems a bit finicky in the descriptions online, I found it reasonably easy so long as you are patient.
I used this approach to make a peanut chocolate cluster and a red quinoa “Crunch” bar. The sous-vide approach to tempering described at Serious Eats seems like an even easier way to go. The same process is followed as above, but allows you to perform it all via a sous vide machine. The chocolate sits in a vacuum-sealed bag and only requires occasional agitation.