Empty the tank
The water extracted from the clothes as they are dried collects in a water tank found in the bottom of the dryer. To get to the container first remove the lower cover known as a plinth. Grasp from both sides and pull off the machine.

plinth being removed
Now you can remove the water tank from the bottom of the machine, as shown by the red arrow. Simply pull it out and drain the water out.

Always disconnect your appliance from the mains before you start examining it!