You will arrive into Terminal 1, clear immigration and customs, come out into the arrivals hall, check in for your domestic flight near the arrivals hall, and then go through to the domestic gates.

After you have come out into the arrivals hall, and before you proceed to the domestic gates, you will be able to use two Priority Pass lounges at Terminal 1 which are landside.

https://www.prioritypass.com/en/Loun...-International