Traveling to US from India on 2 stop flight, 1st being in India. For COVID-19 test what is my first embarkation. Its a single ticket from India to US

If you are on a single ticket, you need to test "one day before departure", which is the first flight in the sequence. Additional rules may apply depending on exactly where your layover are and how long they take.

https://www.cdc.gov/coronavirus/2019-ncov/travelers/testing-international-air-travelers.html

If your itinerary has you arriving to the US via one or more connecting flights, your test can be taken within 1 day before the departure of the first flight.

You also have the option of getting tested en route during one of your connections. However, you should consider where in the connecting airport testing is available and if you would be able to access it while in transit. If you choose this strategy and are unable to get a test en route, you will not be able to board your flight to the United States. You should also be aware that if you test positive en route, you will not be allowed to continue your travel and may need to stay at that location until you end isolation.

Please note, if you planned an itinerary incorporating one or more overnight stays en route to the US, you will need to make sure your test is not expired before your flight that will enter the US. You do not need to be retested if the itinerary requires an overnight connection because of limitations in flight availability.