You don't remove the nuts from the circuit board!!!
You spin off the gold rings with the red and black marks on them off each of the six posts from the rear of the speaker and I think there may be another nut behind that, not sure it's been a while since I've converted these speakers.
Once you free up the crossover (which in your case will be an active 'plate' be careful when removing the plate as their are six plastic spacers between the circuit board and the cabinet, and dropping them inside the speaker makes for difficult recovery! Once you have the plate out, rewire the original crossover and replace it by reversing the steps above.
You spin off the gold rings with the red and black marks on them off each of the six posts from the rear of the speaker and I think there may be another nut behind that, not sure it's been a while since I've converted these speakers.
Once you free up the crossover (which in your case will be an active 'plate' be careful when removing the plate as their are six plastic spacers between the circuit board and the cabinet, and dropping them inside the speaker makes for difficult recovery! Once you have the plate out, rewire the original crossover and replace it by reversing the steps above.