I installed my BlueSea Multimeter just like the one you have right next to the 220 VAC circuit breaker panel. Of course you want to remove all power to that pane before working on it. I was able to insert the wires right alongside the Amel bundle of wires without drilling any new holes. The wires are small diameter as I recall and there was adequate space. Access is gained by removing the 220 panel on the bulkhead. All the breakers/buss/and wires to them will be exposed. Find the main feed wires to the CB (circuit breaker buss bars and crimped or soldered on ring terminals to attach to L1 & L2 (the blue and brown European feed 220 VAC wires). I presume that you have the model with the torrid for determining the amperage. Install it inside the 220VAC gray plastic box on the supply leads as directed in the installation instructions. The wire bundle supply to the 220 VAC panel is stiff so be careful during your manipulations to not break/crack the plexiglass panel or any of the CBs or buss bars. You should have plenty of wire to reach any reasonable installation location.
If you have more questions don't hesitate to ask.
Gary S. Silver
s/v Liahona Amel SM 2000 SN 335
Puerto Del Rey, Puerto Rico