take the plastic tirm off the inside of the boot, disconect the wiper motor, take th bolt out of the wiper blade itself (its pivoting point)
If it doesnt just tug out stop and grab a axe saw and saw it off, high risk o smashing your window.
Then got into the boot and under the carpet in the middle there is a rubber gromit the perfect size just pop that in the hole an bob's youre uncle.