1. Set up your machine
In addition to any usual CLI parameters that you run polkadot with, you'll need to add an extra two:
--validatorThis tells your node to try to validate when it sees itself as a listed authority on the network;
--key <SEED>This provides your node with a secret key that lets it know whether it's a listed authority on the network, and, if it is, lets it sign statements to authorise the creation of new blocks.