To start using NTG, you will need to create them as a carrier.
To do this, go to Connect > Carriers and find NTG in the list. Select it and click "Connect to carrier".
You will now need to enter the following info provided by NTG:
Once entered, all you have to do is press "Create Carrier" and you are all set and ready to start creating shipping methods with NTG.
Once you have connected to your carrier, you can start building your desired shipping rates with each of the services available on the carrier.
Simply navigate to Connect > Order channels > Select your channel > Add Shipping rate.
Read more here on how to build shipping rates.