Depending on the setup of your cloud provider, they may give you an endpoint to use to manage volumes, or there may be an extension under the covers. In either case, you can use the nova CLI to manage volumes.
volume-attach Attach a volume to a server. volume-create Add a new volume. volume-delete Remove a volume. volume-detach Detach a volume from a server. volume-list List all the volumes. volume-show Show details about a volume. volume-snapshot-create Add a new snapshot. volume-snapshot-delete Remove a snapshot. volume-snapshot-list List all the snapshots. volume-snapshot-show Show details about a snapshot. volume-type-create Create a new volume type. volume-type-delete Delete a specific flavor volume-type-list Print a list of available 'volume types'.