I am not intimately familiar with your model but generally you would access it by inserting a screw driver or putty knife in the gap between the front and the top at the edges and releasing clips which will allow the top to flip up (confirm you can do this by looking to see if you have hinges on the top at the back)

With the top up you can vacumn the back of the drum where the heating element is, and even better if you have access to compressed air is to blow out the while compartment, which is what we do.

Good luck