Remove the capsule holder.

Close the lid (as if you were to make a brew)

Insert the small screwdriver at the point shown by the red arrow, press the screwdriver inwards 2->3 mm and the plate should drop down. There is a small spring behind which is moved. The spring sits on the plate. Due to lots of calcium deposits the plate may need a little help to come down.

Insert the new or cleaned plate, latch backend first and click in place in the front.

Once done, connect the device and make your self a brew and see if it is well-deserved. No Leaks - You've earned it. Leaks = You need that cup to ponder where the issue then is :-)