How do I change the firmness?

Zip open the cover and rearrange the foam layers that the one you prefer faces upwards. These layers are colour coded with the grey foam being firm, the blue foam being medium firm, the pink foam being medium, and the white foam is soft. So, if you prefer a soft comfort surface place the white foam layer facing upwards, the sequence of the rest of the foam underneath does not matter.

preference firm softer hard harder