As @Vidyasangar mentioned, ibmcloud target -g RESOURCE_GROUP_ID
will set the target resource group for your current CLI session.
If you want to create / manage resource groups, you should do so under the ibmcloud resource
command (abbreviated):
NAME:
ibmcloud resource - Manage resource groups and resources
USAGE:
ibmcloud resource command [arguments...] [command options]
COMMANDS:
...
group Show details of a resource group
group-create Create a resource group
group-delete Delete an existing resource group
group-update Update an existing resource group
groups List resource groups
...
I hope this helps.