There are a couple of options to return your honey back to a liquid state.
First option is to place the jar (with lid on) into a pot of boiling water until it has reach the desired consistency. This is the preferred method.
Alternatively, you can place your jar of honey in the microwave at half heat for 30 second intervals, stirring between each interval, until it has reached the desired consistency. Microwaving your honey is not highly recommended.