A good way to reheat risotto is to put the leftover risotto into a microwave safe bowl and microwave the risotto.
To use the microwave to reheat risotto put the risotto into a microwave safe bowl and add some more water and then place the bowl of risotto into the microwave.
Turn the microwave on to the high setting and set the microwave to 4 to 5 minutes depending on the power of your microwave.
After a minute or before a minute stop the microwave and stir the risotto so that the risotto heats more evenly.
Otherwise the risotto could stick and burn.
I have always use the microwave to quickly reheat risotto and it has always turned out great.
You could also put the risotto into a pot and slow heat it on the stove after adding some more water but the microwave reheats the risotto just fine and faster.