There are 2 ways to melt chocolate:
Pop your chocolate in a heatproof bowl over a pan of barely simmering water. It's important not to let any water or steam come into contact with the chocolate because it will make the chocolate go lumpy and thick. Heat over a low heat stirring until you have lovely glossy melted chocolate.
Or pop your chocolate into a microwaveable bowl and melt in the microwave for 30 seconds, stir and pop back in the microwave for 10 seconds intervals stirring between each interval until melted.