Are you using a split or solid core CT? It’s much easier if you buy a split core CT. You simply clamp it around the main live feed and don’t need to disconnect any wires.
For the live and neutral for the Pzem you have 2 options:
If your consumer unit is close to a mains socket wire up a plug between the socket and the Pzem. This is the safest as it’s just like wiring up a plug for a TV or a kettle etc. Certainly this would be a good way for you to test your system until such time as an electrician completes the installation for you. If you only have a solid core CT I wouldn’t do any more work inside the consumer unit based on your knowledge of electrical wiring.
Alternatively you need to take the feed from the consumer unit. This is blue and brown from the trip switches but if you are having to ask the question I would leave it to an electrician to do.