@Sangwon_Jake
Checkout this doc 1 and this tutorial 1.
The init_method arg helps process groups to perform rendezvous. You can use either of the following two options:

set with a string. E.g., for local training, you can specify sth like tcp://localhost:23456 to tell all processes to rendezvous on that port.
set MASTER_ADDR and MASTER_PORT env vars.

BTW, for questions regarding distributed training, please add a “distributed” tag, so that the corresponding team can closely monitor that.