Start with one of these. https://www.amazon.com/dp/B0777H8MS8

move it around to all the different outlets you have stuff plugged into.

Next buy a clamp on ammeter and have someone show you how to use it.

https://www.amazon.com/TOPINCN-Digital-Multimeter-Voltmeter-Ohmmeter/dp/B07NPC8Z74

Your big loads are stove, washer/dryer, dishwasher, refrigerators/freezers, ... window AC's

Figure a frig adds $20/month to the electric bill. Dryer can really run up the bill if you have kids and do a lotta laundry. Use a leaf blower to blow out the vent lines, clean the filter before every load.

Make a list of known loads and then identify your unknown ones ---