I was getting the following error on Step 3:
The TokenServiceCapability is not configured in the Content Discovery Service http://localhost:8082/discovery.svc
Found that TokenServiceUrl="http://localhost:8082/token.svc"
is missing from cd_storage_conf.xml from ConfigRepository node
Added and ran the discovery update
java -jar discovery-registration.jar update
And finally the command
Add-TtmCdEnvironment -Id SampleCD -EnvironmentPurpose "Staging" -DiscoveryEndpointUrl http://localhost:8082/discovery.svc -AuthenticationType OAuth -ClientId registration -ClientSecret Reg1str@t10nP@ssw0rd
*Posting here to check if this is the right way