Just continue the guide at https://www.thethingsnetwork.org/article/setting-up-a-private-routing-environment that you seem to be using. The screenshot you “quoted” is just named “Preparation”. At some point you’ll get to:
gateway-connector-bridge --root-ca-file "bridge/ca.cert" --ttn-router "localhost:1900/mynetwork-router"
Also, like written in that guide, any new questions should go to https://www.thethingsnetwork.org/forum/t/setting-up-a-private-routing-environment/4445.